Volvo V50 speed fluctuates with acceleration

Hello municipality, I have the following problem with my Volvo v50: We bought it a few days ago, since everything was still in order admittedly not the most beautiful but no error messages or similar. When we drove it back, we noticed when speeding up the speed fluctuates upwards without the car speeding up great. And once we completely accelerated it, above 4500 revolutions per minute nothing went like a power drop. But if the speed went up to the limiter. Does any of you have any idea what it might be? I read what about a broken clutch or brake fluid or back bearing? I’m still young and it’s hard to have a clutch replaced like this:/ Thanks in advance! ??? Pair of key data: Volvo v50 2.5 t5 2006 BJ 198000 kmh 220 hp manual transmission