You can't upgrade that RAM.

It’s hopeless. If your laptop has 4GB soldered with no expansion slot, you’re stuck with 4GB. No amount of wishing or software tricks will change that.

Laptop manufacturers sometimes solder RAM to save space or cost, and they don’t leave a slot. You can’t add more. The only option is a different laptop — preferably one with at least 8GB of RAM, ideally 16GB, and a slot for future upgrades.

Some people will tell you to try closing background apps or using lighter games. That helps, but 4GB is a hard wall for modern gaming. Your stuttering is almost certainly from running out of memory.

Don’t waste money on “RAM cleaning” software or USB-based RAM things. They’re scams. Save for a new machine.