Gear problems

Hello, have a Laguna Grandtour Bj.97, 2,0 with 114hp and approx. 240000km down. Got the problem that I can get the gears hard in, especially now that it has become colder. Must explain briefly since I noticed this: In July 2014 I got the cuff from the differential where the drive comes out leaking and the oil came out with engine on the beam (if you kick into the engine compartment right side) which was already long Porous and it has probably for some time already some transmission I then had to tow it and to the workshop. They renewed the cuff and filled up oil about 2 liters but 75W -90. So mixed. After that everything was ok until now where it has become cooler there I got the gears hard when I am then danger they went in again without problems. I changed the gear oil now on the past Wednesday the original ELF oil which is in the magazine there is no more but the supposedly better successor version from ELF TRANSELF NFP 75W80. So old oil (were also no metal chips in the oil, at least I didn’t see anything it had but slightly foamed in the bowl) out, new oil in the book stands 3.1 liters but only 3 liters fit in then I didn’t drive with it until today, but had run it warm in the stand and switched on in the stand with engine, without big problems. We had the car in front up-bocked so he just like with normal chassis stand because he in the front approx. 6 0mm lower is. Have 1 day later and today before driving In the stand without engine to the switching tried (cold oil) there the gears went in without problems. I then started and then I got the gears hardly any more into it, only with pressure. I then drove and after a few meters went in again but still a little rough and after a few km it worked again normal. It also happens to me (or maybe I imagine) that if I stop motor from then Moto r on, which goes in 1 gear with a beating noise. Had in between the car parked about 1 hour, engine on then started again car was still warm 1 gear, 2, 3 he etc. went in without any problems. What can this still be the so difficult in the cold go in. Thanks in advance. Greetings.