I have changed the chain after my gauge showed that it's .75 worn. New chain jumps anyway. Why? How to deal with it? I am riding MTBs for over 8 years and either the rules and tools to measure the chain wear do not work or I don't understand how to use them..

I have bought Canyon Exceed with 1x11 SRAM drivetrain. I have been measuring the chain wear and after 1500 km the chain gauge showed .75, which as I understand means, that the chain is worn and need to be replaced, but the cassette should be ok. So I have changed the chain. Well guess what - it skipped on two sprockets. I was shocked. I had the same situation on my 3x9 Drivetrain. there I even tried to change the chain after 500km and the chain skipped on the 2 smallest sprockets. 
I keep my drivetrain quite clean, and lube it frequently, of course this new bike was always washed and lubed..

I don't know what I do wrong.. I expected that the 1x11 drivetrain will help me to avoid this problem, since all the shifting happens only on the cassette side and not on the chainrings.

Maybe some of you have some suggestions, how I can avoid this problem - next to that will the SRAM x-sync 32 chainring (small aluminium chainring) be worn too if I will put the old worn chain again? 

Thanks a lot! Gidi
The previous answers appear to have missed the fact that with 11s and higher drivetrains, the current consensus appears to be replacing the chain once it hits 0.5% wear. At .75%, riders will frequently need a new cassette. While this obviously seems expensive, many 11s and higher cassettes are even more expensive. On the road, our outer chainrings are also very expensive, and we really don't want to wear those.
In comments, the OP said they used a dry lubricant. Dry lubes contain some lubricant, usually wax-based, in a carrier fluid. The fluid evaporates. Some empirical testing has shown that many dry lubes are poor lubricants. White Lightning's dry lube is a particularly clear example: if you examine a bottle that's been sitting on the shelves, you'll see that it's mostly a clearish fluid, and a small amount of residue at the bottom. The residue is what dries off and lubricates the chain. In a wear test of White Lightning Epic Ride, Adam Kerin agreed that it made for a clean running drivetrain. The price of this was one of the highest wear rates he has tested. He described the test chains as sounding dry very quickly, which is an indicator that there is not much actual lubricant in the chain.
High-performing dry lubes (i.e. produce long chain life and low drivetrain friction) do exist, but they require very thorough cleaning of the chain before application. This involves repeated solvent baths, and preferably removing any solvent residue with an alcohol bath afterward. I think that the OP's choice of a dry lube probably shortened their chain life. I would suggest switching to a good wet lube. If the OP just does the same chain cleaning routine described in the comments, I bet this would produce markedly better chain life.
If the OP wanted to go one step further, I think that an on-bike chain cleaner is relatively simple to implement. I am not sure how much difference wiping the chain with degreaser on a rag makes; what you ideally want to do is to get the dirt off the chain surface and out from inside the chain, at least as much as possible. A rag and degreaser shouldn't clean inside the chain. I'm not sure if it will remove more dirt than simply wiping the chain.
Fun fact: in chain wear testing, i.e. when comparing different chains (as opposed to different lubricants) for durability, Kerin now uses White Lightning dry lube to shorten the chain life, so that he can complete the tests in a reasonable interval. To my knowledge, he only has one test rig.