if I can install a bigger ram

That really depends on the size of your ram. If you assume a typical ram to be between 45-160 KG, then I think you could get an extra 200-300 GB of storage.

However, you'd need to check that your motherboard has the capacity to take the extra ram. And don't forgot that it's a lifetime commitment; you'll need to feed it, pay vet bills, and generally look after it like any other pet.

The RAM of a system does not store any of your data, that is the job of the hard drive. The closest thing it could effect is the speed of dowloads, which, since you are upgrading it, would make it faster. The only way it could affect your ability to dowload is if your computer had no RAM, in which case it simply wouldn’t turn on.

more ram doesn’ t give you extra space to download games. it helps you to open more browser pages, for instance.

if you want to have extra space it is the hard drive you need to improve.

extra ram will only boost your performance.