Problem with screen and performance issues

Hi

I have a new XPS 15 9570 since July. These are the specs: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz, it has a 4K monitor.

First some history... The first days/weeks I experienced some problems with my screen. Now and then (rather almost every day) there was a gradient going from normal colors to black. Dell support could not find the cause and therefore they replaced my screen very quickly. Now that's okay.

But I have to say that in general the colors of the 4K screen are actually strange. Mostly in the dark parts it seems as if the screen cannot display this and it is as if a 'hollow' black is being shown. Is this normal? What can I do about it?

Apart from that, I experience another problem. I edit my photos in Lightroom, but when I want to display them fullscreen on my laptop (no external screen connected) my computer freezes. It's almost every time.

My laptop also has a difficult time when I'm browsing through my pictures fullscreen on Lightroom. For the record, there's nothing wrong with Lightroom. It's the Lightroom Classic version of the online Adobe Creative Cloud solution.

With freezing I mean that there's a black screen with the words 'loading' and it's flickering and this may sometimes take about 10-12 minutes. There are no other processes running at the same time.

When I open YouTube at the same time I'm working in Lightroom the problem is even worse. Than everything goes so much slower and it's really not workable.

I find it quite strange with the specs I have. Even my previous Dell, that is 8 years older is faster when previewing images and watching YouTube at the same time.

I was always quite happy with Dell, but my experience with this laptop is rather negative. 

Now I tried to contact Dell for this issue to get some help. They promise support on Saturdays till 8 PM, but it's already 2 Saturdays in a row that they mention that they are closed (after going throught the whole telephone menu).

I'm quite stuck. Has anyone else experienced this issue? And what can I do about it? And yes, I've updated all the recent drivers and downloads