Problem with installing new Forge version

[Felippemns089]

Hi there!
I have currently a problem with installing Forge.
I was playing on 1.12.2 version with Forge, Optifine and textures - everything was fine. I decided to install 1.8 version with Forge, because some days ago I started playing more pvp games.
I installed Forge 1.8, but it was crashing - maybe because I still had 1.12.2 version.
I thought then I just have to delete the Forge 1.12.2 in version folder+mods folder. Did it, and tried to install Forge 1.8. Well... Every time Forge installer is stuck at "tried to unpacking library folder". I tried to delete the libraries folder, tried to delete Minecraft folder, tried to uninstall Minecraft. Did it multiple times and nothing works.
Maybe you will say that the 1.8 is outdated, but wait - like 3 days ago I told my friends to install 1.8 version Forge, they did it and everything was fine. And, they had "blank" Minecraft before that install, without any installed Forge before.
Is the old Forge in folder somewhere? What should I do?
Please help ASAP, as I am trying to get high level in BedWars before the holiday but I am stuck.
Tysm, Feli