I really like Aric mod but When I have multiple servents it is so hard to develop fetish . Can I somehow edit mod so allways it succed?

It is recommended that you make a personal backup of the file being edited and the save file in case mistakes are made.  I don't know the full structure of the mod so I don't know of the side effects, but it is pretty easy to find the fetish system. 

In the Strive program folder find person.gd (".../files/scripts/person/person.gd") and open the file with a decent text editor. Find the line that starts with"func checkFetish" (line 1277 in my file), then find the line "if rand_range(0,100) <= 20 + ((opinionrank*10) * clamper):" below it (line 1292). Change that if statement line to "if true:" to guarantee success when encouraging though this will effect a lot of systems. Try not to mess with the leading tab or the new line characters as godot is very specific about its whitespace. You will get a parse error if those get messed up.

Alternatively, the talk menu is found in the Strive program folder find statstab.gd (".../files/scripts/statstab.gd"). Find the lines that start with "func talkFetishEncourage" and "func talkFetishDiscourage" (lines 1677 and 1707), then find the line "if person.checkFetish(mode):" below each of those(lines 1688 and 1718). Change that line to "if person.checkFetish(mode, 8):", to probably guarantee success unless the person has an opinion score less than 1 of the fetish. While maybe not guaranteed to succeed, this method will not effect other systems.