Computer slow and frozen after downloading java and android

Hello,

I am new to developing, I bought a book to help me learn, after downloading a few programs my computer has been near unusable. I can no longer launch steam or other applications, the computer freezes.

I downloaded virtualbox, a java sdk and various files, the android developer studio, android files.

Last night I was using android studio designing an app and it worked fine. I started getting a lot of lag when i closed all of the programs. I think there may be something with the virtual machine taking up soo much ram but I have no clue what is wrong with my computer. I realize I may hve made a mistake by not using a flash drive for all of the programming and developing files..

I would like to get my computer back to running smoothly, I am not sure what the problem is. Please help. Tips about where to put these developer files would be appreciated.

I have erased and uninstalled all soft, I have about 8 GB in files I would like to remove, I have cleaned my pc using that method three times now. Everytime I go back into clean pc, the files are still there. System has been starting to crash now as well.