Hello,

First backup your files from phone if you need anything.
Here is language description,click on link: Top Sony Forum - Languages Description
Post here identify log from your phone with setool2lite.
If your phones working good there is no need to flash them because there is always a risk so the choice is yours.
If your phone was unlocked by patch then it will be locked again after flashing because flashing erase patch so you will need original sim card that phone is locked to be able to unlock it again.
I recommend you to use search button and read a lot about "K 750 flashing" and "K 750 unlock".
You can't read flash and flash another phone and all files you need are in download section.

Regards