OK, here are some thoughts on this:
-- Has the lens been serviced? It's possible that it was incorrectly reassembled. That is easily fixed but requires disassembly of the lens.
-- Is the lens collimated? At the least, infinity focus should be checked with the lens set to infinity, with the shutter open and a piece of ground glass on the film plane. You can also you some frosted tape. Use a loupe or another lens to check focus.
-- With some German cameras, you adjust infinity focus in the viewfinder by altering the angle of the mirror. But I just checked, and this doesn't appear to be the case with Exaktas.
-- Check to see that the viewfinder is fully seated.
But if that were my camera, I would start with the viewfinder, then check infinity focus at the film plane.