Aisles can sometimes be badly inserted ÖL????

Problem: Especially the 1st, as well as the reverse gear can be badly inserted. When the car is cold it goes better My read knowledge: Although actually maintenance-free it can not hurt to change the transmission oil. Especially because allegedly before 1998 Opel was not used so good. Lots of 1.2 L. Old oil out, new in, 0.5 hours drive, let off again and refill again. It should get better and become even better with increasing time. Which oil to use My car parts business had not found a comparison product in the computer… Special Opel. However, if the old original ÖL on the net is called a plürre, what comes in can only be better, and took the most purchased VALVOLINE ATF TYPE D. At first it got a bit better but now, after my holiday trip it has become much worse. Sometimes I help myself by first inserting the 2nd gear and from there from the 1st who n the first time is against bucky someone knows this symtom and what was the cause? What oil do you have in your slurry gear? Should I tilt an additv? Thank you in advance