@tayfunmutlu on here we are more the hardware kind of crowd :-) Make sure that you have a Sim card that is actually working. You can always check it with another phone. I suggest you check with the forums that deal more with firmware/software issues etc. Something like [https://forums.androidcentral.com/|Androidcentral] or even [https://xdaforums.com/|XDAforums] might work better to get your firmware /software issues resolved.