Good morning mehmetcirit,
I know what you mean.
A couple of years ago the same thing happened to me, i was working on a project of reverse osmosis plant, by that time i made a big an complex routing of chemical pipes with different specs. I wanted to enlarge or shorten a little segment of that routing, but the whole pipe of the reverse osmosis plant moved as if the elbows where welded and didn´t allow the different segments of pipe move on a free way.
Sadly, i couldn´t find a solution about that issue, if i wanted to enlarge or shorten part of the pipe routing, i had to delete a little segment, latter i enlarged the required segment and finally joined the 2 separated parts of the routing pipe because of the little segment previously deleted. It is a little bit time consuming process, but so far, i don´t know a solution.
If you want to avoid this kind of situation you have frecuently to purge unecessary elements of a drawing, daily cleaning the cache of your computer, etc...