Władimirec T25 from 1978. - the gearbox is stuck

Hello everyone, I am a young farmer who bought a T25 tractor from 1978 with two couples. I need help because the gearbox is stuck. Of the four rollers, the first two are reared and no force moves them. Unscrewed slides, gear rods extended. I don't know what to do next, all that's left is to unscrew the top sheet under the wires. Please help. I will add that after blocking I pulled him with a second tractor, wheels one to the right and the other to the left. I greet arthur

You twisted something but maybe try to adjust the gear block

Hello. Thank you for all the hints, I check everything by defending myself against unscrewing the top cover of the gearbox.