Transmission. If automatic, be sure to check fluid. Also may need a filter change. If a manual, check the clutch is fully engaging. If so, then clutch is probably burned. Manual is cheaper to fix.
I was driving to my house in the mountains(going up hill) and I was in fourth but it didn't feel responsive and I would push on the gas and the rpm would go really high but barely increase speed. so I tried the other gears which also felt similar, sluggish acceleration and high rpms. The last hill to my house is steep and it barley made it up in second at 4-5 thousand rpms. I stoped in neutral at my house and there was a really terrible burning almost plastic or something smell. I assumed from such high rpm. The neutral idle was 1.3 rpm which seems higher then normal. The next day drove it down the hill and felt a little more responsive but probably because I was going down hill. Any help is much appreciated I'm a student who prays my transmission isn't bad or something gotta get to class and I'm broke.
Thanks for listening!!