Tyre won't deflate completely/starts inflating itsself at a certain point I noticed a flat tyre on my bike this morning and wanted to change/patch the tube. But now the following problem arised: I don't seem to be able to completely deflate the tyre, after it hits a certain point, it immediately starts to inflate itsself again to an equilibrium. Furthermore, the valve (sclaverand) may be damaged, as can almost normally deflated without even opening it (the same problem with self-inflation happens here, too). When the valve is closed, the air comes out of the valve-hole in the rim. Do you have any advise, how to get the tube out or rather the tyre of the rim?

What you most likely have is a tyre with very stiff sidewalls AND a very tight seal on the rim.

The tube is no longer inflated (hence your experience with the valve) and the air intake you are experiencing is a result of the stiff tyre trying to regain its shape and sucking air in at any point where there is not an air tight seal (so likely either the valve hole or valve itself with a punctured tube).

When tyres are a super tight fit on the rim, there is a technique where you can lay your wheel flat on the ground (somewhere soft like grass is best to avoid scratches) and stand on the tyre (not the rim!) with your heel. This should be enough to break the seal with the rim and get tyre levers in to remove the tyre.