i installed the client but its show a bug even before opening the client
You can bug report it here: Gaijin.net // Issues (just search a bit first so that you don’t report something that is already reported and known about)
A guide on how to report bugs can be found here: ([Navigation] Technical Knowledge Base | War Thunder Wiki)
Try deleting the cache folder within WT. It’ll rebuild it on start up. Might solve the issue.