You got rockets equipped. When rockets are selected the sight changes to the rocket sight to help with aiming. To get rid of it either change secondary weapon or get rid of them.
Sir！ What I mean is that the position of this rocket level gauge is incorrect and crooked
Have you looked at this setting called “vertical targeting” (available before you enter test drive or spawn in a match):
If you are certain that the sight is incorrectly placed then you can bug report it here (just search a bit first so that you don’t report something that is already reported and known about): (Gaijin.net // Issues)
A guide on how to report bugs can be found here: ([Navigation] Technical Knowledge Base | War Thunder Wiki)
Oh I’m sorry. You didn’t give any context so I assumed from the very little the topic title says that you meant the sight itself and not its position. I unfortunately don’t know how to change its position or if it’s wrong/bugged.
The rocket guide isnt really accurate for anything until modern jets which get CCIP (Constantly Computed Impact Point), even then its hit or miss. You have to just go by feel.
It is “crooked” because you are not in level flight - the rockets will fall somewhat to the right of straight ahead, and so the rocket aim tool is reflecting that.
It isn’t very accurate - but it is useful - the lines equate to 200, 400, 600 and 800m range