I have fixed the problem.
Key objects are:
F_FICA_CCT
F_FICA_CTR
F_FICA_FTR
Since I want my restriction to be on Funds Center, I did it like that:
F_FICA_CCT
F_FICA_CTR
Activity 20 and 21 for all higher level nodes, fund centers in the structure including the one the users has to work on
F_FICA_FTR
Activity 21 for all higher level nodes
Activity 20 and 21 ONLY for the fund center the user belongs to
Cheers!