Speed doesn’t go down right now

Moin, just in advance, does not come to my computer at the moment and can only get in via the app here, search me there misstatement. The following problem. I drive completely normal and want to switch up from any gear to the next, the speed does not fall off when uncoupled but increases for a short time. If I completely uncouple to stop the speed remains also short increased, but then sinks down to the normal idle speed. This phenomenon occurs only if it is dr outside is very warm, over 30 degrees as it is today. I know the summer is over from tomorrow, but I’m interested in where it might be. Greetings Flo