I then researched and found that one may never use frying oil which is not suitable for frying, which then gummy at high temperatures a bit on the internet. That's what I have unfortunately made many years.
Then yesterday I wanted to buy a new frying pan into the city and told the clerk about my problem. She thought then that I should not buy me any new pan, one could make the coating of the old well again: boil water with vinegar and then possibly still hernehmen a special cleaner by Silit.
At home, I then boiled in a pan with vinegar water (I had no vinegar at home), all have a bit of acting and then washed with a sponge and dish soap. Then I still have a bit of research - the special cleaner is probably just soda. Soda I had not at home and have instead baking powder hergenommen: boil water with baking powder in the pan and let stand a bit. The whole then rinsed again. In the manual of the pan is also noted that one should bring to a boil in a pan with salt water if the pan is dull (whatever is meant exactly dull). Can not hurt, I thought to myself, as well as made.
I then equal fried an omelette in the pan and in fact, it works again! Unfortunately, not quite as good as in the beginning, but good enough. I do not know what that has now caused exactly by the three steps, I did not make any interim tests, but the important thing is that it works again.