Need help from professional BS

I am so confuse about lv up of BS skill
Does create equipment skill hav more lv mean : more success rate or more potential recieved
Dose upgrade equipment skill hav more lv mean : use lower potential to add stat on equipment
Dose craft skill hva more lv mean : i can process much more material when process success or increase success rate of process (and if i failed when process a stack of something mean i will lost all of it? )
And the last one, am i correct : Tech stat increase success rate when i create equipment but the potential of equipment i create will lower bcoz of loose some stat(ex.vit10for 1potential of armor) to up Tech stat instead

Thanks you.