Welcome Haribo!
How old's your DS? Ours started protesting naps around 2 years plus something (??) but still definitely needed them and is still going now - just! Whenever he would start to struggle with his nap we would push it out another 15mins, then he'd get down more easily. We were also quite firm with him about having his nap, he knew we wouldn't give in. We did this because on the rare occasions when he had to manage a NND, he was seriously flagging by 3pm! If BT was suffering we'd shave 15mins off the nap. This worked until we got to 7h A time with 45mins nap, then we went to 1h set nap time so would wake at the same time regardless of when he went to sleep, he has a gro clock so knows when it's time to get up. Nowadays if he's awake when I go to put DD down he'll just get up anyway, which is fine with me, I just think I'll find routines easier to mesh if he keeps his down/nap time until DD has dropped her 4th nap... Which should be soon! Even wondering whether to go CT once that happens and just let him tell us if/when he thinks he needs one???
Hugs Aishi sorry can't advise as have no experience of set A times at this stage, we've done set nap times since the 2-1.