SSD GEN 3X4

The Lexar page has this product description statement on the site for the NM800 (I assume you meant the NM as a search for an NW did not turn up a Lexar product).

"Designed for hardcore gamers and creative professionals, the Lexar Professional NM800 M.2 2280 NVMe SSD provides maximum SSD performance with speeds up to 7400MB/s read and 5800MB/s write1. It’s supported by the PCIe Gen4x4 NVMe 1.4 technology standard and backwards compatible with PCIe 3.0."

Overheating would definitely cause freezing and not knowing your Dell model number, you did not post it, a heat sink and thermal pad may be required.

Apologies for the error, using a Dell vostro 14, on the manual it says pcie 3x4 compact able.. but my SSD is gen 4x4

That could be an issue right?

No -- x4 drives are backward compatible.  High performance drives generated more heat - in a tight chassis like a 14" business system, that is more likely the issue:  overheating.

So did some observations and here are my findings;

1. Either this nm800 pro is too powerful for my motherboard or the drive does not support it...

2. I can only do light stuffs, web browsing , not even a low demanding game will run on it, it's that annoying...

I need help guys, am literally dying. Thought the SSD would make life better, no it hasn't.

What information can I provide to assist in helping me?

Check the power requirements of the new drive.  They're likely substantially higher than the original's.  If so, return the high performance drive in favor of one that draws less power.

So as I was getting massively frustrated with the SSD, oh before I forget , it doesn't get up to 7gb read speeds, it's capped at 3.5gb, incase anyone wants to buy...

So what I did was I removed the sticker on the SSD, did the same thing I was always doing, playing games, running programs , general use, and altho it was still getting hot, but it doesn't freeze anymore. Don't know if it's a good thing but it worked for me.