Hello,

I'm new here. Bought a used bicycle recently, you'll find the details of the bike in the attached picture. I live in Aachen, Germany and there are a lot of slopes, so gears are very important. When i bought it, the chain, rear gears and gear cables were very rusted. The person who I bought it from suggested that I oil the chain and gears twice within a gap of the first 3 days, and it will become alright. Tried what he said, it worked. Now it runs almost completely noiseless. But the gear shifting on the rear wasn't perfect. Some gears didn't engage correctly, and there was an offset, i.e., the switching to 7th gear would actually put it on 6th gear, 2nd gear puts it on 1st gear, and 1st gear would make the chain fall next to the spokes. I watched some videos on adjusting the rear derailleur, and made some adjustments to make sure it didn't fall off, it works. But still there are problems with shifting, like sometimes it doesn't engage on a particular gear when switching down, but engages when switching up, doesn't go to the 7th gear at all when the front is on 3rd, completely skips the 2nd gear, etc. Checked the cassette itself, and there don't seem to be any obvious problems, like breaks or cracks. I'm not sure whether it's a problem with setting up the cable tension, limits, etc. or the parts itself. Can anyone please advice if I should look to replace the parts or if it is possible by just adjustment? Will post more photos if necessary