I keep getting this error where it says "Failed to load schematics" everytime i press load schematics i have tried this with different versions of litematica and different schematics but i kept getting the same error. Im quite new to litematics or schematica and have very little experience so lord have mercy and help me please.

This is now fixed/implemented in the 2021-09-06 build for 1.17.1.

Those schematics are very likely in the Sponge schematic format, which is for example used by World Edit in 1.13+. Currently only the 1.12.2 version of Litematica can directly use that format. Support for that schematic format will come to the 1.13.2+ versions of Litematica with the next update from 1.12.2, but that is still a little while away.

So for now to use those, you would have to paste them to a temporary world with World Edit, and then save them from that with Litematica. Here is a quick howto on doing the pasting, if you are not familiar with World Edit: #265 (comment)