some problems I am facing in my XPS 15 7590

Remove (4), the Windows 11 beta, which is just that -- beta software.  That could solve (2) and (3) as well.

As for (1), blocking the cooling system with a soft mattress or bedding will indeed cause overheating, just as you'd overheat running a marathon on a hot day in a ski suit.  Use the system on a hard, level surface with provision for air flow and you won't have the overheating problem.

Hi,

1) When you say you keep your laptop on your bed, do you place it on a hard surface (like a laptop stand) or literally on your bed? If you're placing it on your bed, you're effectively blocking the fans and they can't suck in enough air too cool down your laptop properly, hence it begins to overheat. By doing so, you're also causing a faster build up of dust and other debris in your fans which means that they will be less efficient at cooling your laptop until you clean them. 

Don't place your laptop on soft/uneven surfaces to prevent blocking the fans. Instead place it on your desk or a laptop stand/books etc. 

Also, how long have you had your laptop for? You might need to give it a clean inside. Use compressed air to clean each fan whilst holding the blade with your finger so that the fan doesn't spin. (If you don't hold it in place and the fan spins whilst you blow the compressed air at it puts more stress on the bearing etc of a fan which could damage it). If you feel comfortable with openening up your laptop, then you can also repaste the cpu/gpu with new thermal paste and also take the fans out to clean them (this way you'll be able to clean them better). 

2) Several users (myself included) also had this problem and a thread along with a solution was posted here on this board: https://www.dell.com/community/XPS/XPS-15-7590-touchpad-does-not-respond-sometimes/m-p/7778544#M76491

You can use the search bar to look up things like this and see if any of the solutions work for you before posting a new thread asking about it.

3) Does it work when you use the camera app for example? Have you checked if you access to the camera has been blocked in windows settings? Settings>Privacy>App Permissions>Camera>Allow access to the camera on this device>click on "change".

4) Did you try connecting a different pair of headphones to your laptop? Do they work? If other ones do work, try connecting the earphones you're having trouble with to a different device (your phone or other computer etc) to see if they're not broken. 

Check your sound settings to see which output method is selected.

Since it's a beta version of Windows 11, bugs like this happen often as the OS is not as stable yet. It might be that your problem won't be resolved until Microsoft adresses it themselves.

I hope some of this might have helped

You may want to consider changing the thermal paste, lowering the voltage on the processor, shutting off turbo boost, and also lowering your processor speed so that the combined speed is below 3.4 ghz   There are other posts on the net that suggest the thermal paste is defective on this model, but this hasn't been verified, and Dell refused to change the thermal paste after I returned my laptop for thermal problems.  Other posts by Dell indicate that changing the thermal paste isn't a service they provide, but I am at a loss as to why since the laptop is under warranty.  Shutting off Multi-core is another possibility if all else fails.