buying notebook :p

[Boop]

I have bad experience with my own old hardware in terms of performance.
No matter how much advice or research you get, used hardware probably won't manage to do the clean 60fps on simple games anymore even if it was at one point set out to do it just fine.

What you need to do is get in contact with or find sellers who offer some recent benchmarking of their hardware. Best case with the exact game/software you want to use on it - because C/GPUs can age really badly

Citation? This doesn't sound like real life. I mean, these things should either work, or fail. Their performance cannot just drop. Maybe your old hardware was full of dust so it would overheat and throttle itself. Otherwise they should work at their original speed. Sure, maybe the silicon degrades, but the "speed" depends on the clock rather than actual switching speed of the individual switches in silicon. Either everything keeps up with the clock rate, and then it works at the original speed. Or it can't keep up with the clock rate, then it just doesn't work.

Ontopic:

Unless you find an insanely good deal on a laptop, I doubt you will be able to run CS:GO at a constant 60 FPS. It's a new game, you can't run it on low-end, previous gen hardware (especially on a laptop). The video linked by STM probably provides a pretty accurate CS:GO experience, except yours will most likely be slightly worse as you have the mobile version of the graphics card (which always perform worse than their desktop counter parts).