Refresh rate stuck on 30 hz - external Dell monitor

@Bartkubisiak  The Vostro 3500's HDMI output only supports HDMI 1.4, which supports 2560x1440 60 Hz or 4K 30 Hz.  I don't think it supports 3440x1440 60 Hz, although given that HDMI 2.0 didn't arrive on laptops until about 2018 if memory serves, I'm also not sure how you managed to run that display at its native resolution and refresh rate from your 2014 MacBook Pro, assuming you're absolutely certain about the resolution and refresh rate it was using AND the era of your MacBook Pro AND you were using the MBP's HDMI output as you are here rather than its Mini-DisplayPort output, which had different capabilities.  As for HDMI 2.0 isn't on your brand new system even though it started arriving in 2018, Dell's 3000 Series systems are their entry level, so those systems sometimes hang onto legacy stuff.  At least until recently, some 3000 Series systems still had at least one USB 2.0 port rather than being purely USB 3.x, and some lower-end Inspiron systems are still using 10/100 Ethernet rather than Gigabit, which has been standard on Dell's business-oriented Latitude systems since at least 2003.

However, since the Vostro 3500 seems to be available with a USB-C port, if you've got that, then the easy fix here would be to use a USB-C to DisplayPort cable.  However, Dell's product page for the Vostro 3500 indicates that the USB-C port is optional, so if your particular system doesn't have it, then you may not be able to run that display properly from that system.

@jphughan thank you for you reply.

I'm sure about the refresh rate on my Macbook Pro 2014 (I connected it through the same HDMI cabel). That's why I was very dissapointed and surprised when I got the Dell laptop. I thought that with the new technology and same brand devices everything should go smoothly.

I believe my version doesn't have USB C port. Can't find it anyway.

Why in the "Supported Modes" in the Intel APP it shows it's possible? 

@Bartkubisiak  I'm not sure what you mean by scaling and optimizing.  I suppose you could try running a lower 21:9 ultra-wide resolution like 2560x1080.  That would run at 60 Hz over HDMI and the display might scale it up.  But then you're losing workspace and even though the proportions of those resolutions match, you'll still have some scaling issues inherent to any LCD display when running below its native resolution, so that really wouldn't be a great experience.  I wish I had a better answer for you here, but I can't entirely account for how your MBP is achieving 3440x1440 60 Hz while your Vostro can't, and since you don't have a USB-C port, the workaround I suggested isn't available.

@jphughan So there is no possibility that I could somehow scale it and optimise it? I don't really need a good graphic. I'm using it only for work. 

@Bartkubisiak  Did you check the actual resolution and refresh rate the MBP is running to that display?

@Bartkubisiak  Sorry, missed the attachment since it didn't load initially.  Ok, in that case I'm not sure what's going on unless the MBP is sacrificing color bit depth and/or chroma in order to maintain resolution and refresh rate, while Windows won't allow that.  The Tech Specs of the mid-2014 MBP 15-inch here indicate that it is limited to 30 Hz on "consumer 4K" of 3840x2160, which is consistent with HDMI 1.4, and which I wouldn't have expected could run 3440x1440 60 Hz, at least at the default 8-bit color and 4:4:4 chroma.  If it can, then I'm not sure what's going on with Windows.  If on the other hand your MBP is in fact dropping to something like 6-bit color or 4:2:0 chroma, then I'm not sure if you can force Windows to do that.  Sorry I can't be of more help here.

@jphughan I couldn't see anywhere that different resolution nor refresh rate is showing. Moreover, when it's running on Macbook the cursor and everything else is NOT laggy, only on Dell laptop. 

Games on Macbook are also running in 4K.

@jphughan It's Macbook Pro 15 Retina mid 2014. It's working perfectly fine. No delays at all....With my Dell it's slightly delayed (mouse cursor is slower).

@jphughan I was thinking, if I could get any adapter to connect it through USB C?

USB-C adapter through USB and then connect it to the monitor? Will it be better than HDMI? 

@Bartkubisiak You said you don't have a USB-C port, so I'm not sure what you're asking here.  Do you want to know if you can use a USB-C to HDMI cable but connect the USB-C side into a USB-C to USB-A adapter so that you can plug that into a regular USB port?  No, that won't work, because USB-A ports do not support video output like actual USB-C ports can.  The only way to get a video signal out of a regular USB port is with a dongle that uses "indirect display" technology like DispayLink -- not to be confused with DisplayPort.  But DisplayLink comes with several potential drawbacks that I've written about in the post marked as the answer in this thread, and I'm not even sure DisplayLink's software supports ultra-wide resolutions.  But if you think those drawbacks might be acceptable to you, then you might want to do some research on ultra-wide support.  DisplayLink has its own forums.  And if you decide to buy an adapter, Plugable is a company with a solid reputation for quality products that makes those types of adapters (and a bunch of other stuff).

I read the whole conversation and my own question is what about the Dell ultrasharp.  On the website, it says the Native Resolution at 5120 x 1440 at 60Hz but unfortunately, it doesn't provide 5120 x 1440 at 60Hz with HDMI only with Type C Thunderbolt 3. Was kind of disappointed but anyway.  The only inconvenience with that is it simultaneously charge and display your laptop which is quite not good for your laptop especially if the power delivery is higher than 90W. Dell Ultrasharp 49 In only provides 90w to your laptop which will drain your battery lives if it is above 90W.

Hi i do not want to set up new topic. I got WD15 and Latitude 5310 with USB C. I recently bought display IIyama GB3461WQSU. This is only display plugged into hub. I tried almost everything cable configuration etc and maximum resolution which i can achieve is 2560x1440. I do not know how to force to change to 3440x1440 even at that 30hz. Any clues?