Flashdrive/steam/ idk completly

Im having trouble with my PC games, please read all of this and understand im not too sure if the problem is my 32GB Sandisk or if its something else...

I am like most gamers who play steam EXCEPT i domt have internet for my computer... So how did i get steam and update it? Well i have a laptop, and so when i go to my grandmothers or my freinds house i connect to their wifi and then use the flashdrive to transfer over my steam folders from my laptop to my good computer. Things have been going fine but now its not... For some reason a certain game called Subnautica kept saying error loading data folder (or somin similair) in Build18.... So yeah, i stopped playing that game after i started getting that.... But i also noticed Banished was not showing up new mods i downloaded from steam, so what i did was look for the mod data files myself... I found them and put them all on the flashdrive and transferd them... So i noticed that basically, my flashdrive wont copy ALL the files, that are in folders.... I think if i copy each data file myself and recreat all the folders on my good computer then subnautica and some other games MIGHT work...