I had a problem with the pack, the size... I need to correct it but I can't, can someone suggest me a way to remove some folders of units in the factions ? 
You delete units from the faction like how you delete a normal folder. However, it is likely you will get errors doing this for which there are no uniform methods to correct.
If you're getting errors when you delete the folder, that means there's another unit/ building/ upgrade/ resource that requires this unit in the faction. You then have to remove all mentions of this unit in all the xml's in the faction.
Hint: suppose you want to remove the cave_spider. First delete the cave_spider folder. Next, open a terminal in the faction folder (NOT the techtree folder, the faction's folder inside the techtree) which contained the now-deleted cave_spider folder. Next, type this into the terminal:
grep -r -l "cave_spider" .This command will list all the files in the faction which contain the word "cave_spider". You then have to manually fix these files. If you want to delete a different unit/ building, it's the same process but delete that unit's folder, and replace "cave_spider" with the unit you want to delete.
Unfortunately, there's a few different types of errors that might pop up which require different fixes.
Another thing I noticed, your faction folders are full of
.xml~'s (probably backups generated from using gedit). You can delete these by going into the top directory of the techtree in a terminal and then recursively delete them:
find -name '*.xml~' -exec rm -f {} \;
