Best thermal paste for Dell XPS 15 9550?

What thermal paste has shown best results for your XPS laptop?

Or anything I can do to speed up my XPS, besides cleaning out dust, and applying thermal paste?

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My 2017 Dell XPS 15 9550 was extremely fast, but has significantly slowed down to a crawl sometimes, very choppy and laggy.

I can't afford a new laptop, and a friend said to clean out the fans from dust, and also to apply thermal paste to the CPU.

I cleaned the dust from the 2 fans / vents / inside, and it doesn't sound like a vacuum cleaner anymore (fans were running full blast all the time), but it still runs slow, and at idle with only my browser open, it's still running hot (55C-70C).

Stats below: