hydrostatic transaxle takes off slowly

I have an old 1990s murray select series lawn mower with a hydrostatic transaxle. I did adjust the linkage from the gas pedal to the transaxle so it can go slightly faster. But after that, every time I would want to drive it, I would have to hold my foot down on the gas pedal for a couple of minutes before it starts to move. Is this a problem with the linkage from the pedal to the transaxle or did I mess something serious up

Sounds like your drive belt is slipping.