18.04 - How to free up the memory in the best way

I'm using Ubuntu 18.04 and 4GB RAM with CPU 4.
I don't have too much memory left, so my computer works slowly and crashes. What would you recommend me to remove from directories? Or some command other than apt autoremove and apt autoclean because that's not enough. I have nothing to uninstall from the Ubuntu Software because there are only the most important things left. Please help :(

There's a couple things you can do. Some of them were already outlined in How can I improve Ubuntu overall system performance?. Here's a few simple suggestions you can try right now:

1. Switch to a lighter desktop, you don't need to reinstall, you could just install a desktop session such as xfce or install metapackage for another flavor, such as Xubuntu edition with sudo apt-get install xubuntu-desktop




2. Add more swap, either via partition or swap file. I've a script for adding swap files to make that process easier.




3. Configure swappiness to help the system handle memory-intensive apps. See also: SwapFaq




4. Disable certain services. Which services to disable will depend on your needs.




5. Buy more RAM. Make sure you buy modules with correct frequency and type.



6. Consider tuning resource usage for certain processes and niceness values


7. Consider some of the cleanup suggestions. BleachBit is a well-known and pretty good utility for that.