what did you record with?

Your computer is a laptop?

If you have your computer for a long time, the thermal grease (dt. Wärmeleitpaste) might have dried out. Perhaps you know a technician who can replace it.

Use a new Computer... (No laptop if possible, especially this cheap trash <900€) It's nothing special that old laptops getting hot as fuck. Beside the termal grease, the wearout of the fan is the main cause for overheating. It's important to clean the fan, the heat pipes and heat sink regularely to keep the cooling system functional. It's also important that the vent slot is not covered for longer time. (Using the device in the bed and stuff) Otherwise the heat can not be dissipated and the hardware get damaged over time.

Btw:

The recording performance depends manly on these factors:

-CPU speed/usage(keyword: background processes)

-GPU speed/usage(keyword: window manager)

-features of the CPU/GPU(some screen recorders using hardware acceleration)

-amount and speed of RAM

-speed of the hard disk/hard disk bus

-usage of the hard disk(do you record to the system drive?)

-dimensions of the recording area

-compression/codec of the video file

-quality of the recording tool

-the weather

-mood of chuck norris

 Apart from that recording speed critical games in linux is a pain in the ass.

Just buy a desktop PC instead of a laptop, you got much more performance for a lower price. It's also upgradable if you did it right so you just have to buy some new components, instead of a damn whole new system.

Overall you should get familiar with the basics of the PC hardware stuff. There are tons of information about that on the web.(I could write a huge post about that but other ppl elsewhere already did) If you know some basics, you can compare the components and make your choise depending on your requirements. It's easier than it seems.

BTW: Pay attention to the linux compatibility of the hardware. Just google "<hardware> linux issue/compatibility"