Rooting does not prevent turning off WiFi, so you must have messed something up (possibly using root privileges to do so, or maybe during the rooting process). Therefore as @ocnbrze
says we need to know what you actually did
in order to help you.
In fact I'd add one further request: don't just tell us which guide or video you followed, tell us what you actually
did. Because if you skipped a step, or used a different file (e.g. a custom recovery intended for a different model) then the guide you used won't tell us that and so we still won't be able to guess what went wrong.
If we can't figure it out then your solution will be to completely reflash the whole device with stock software. This will undo the rooting, but should also undo any mistakes. How you do this depends on what device you have. Of course if you used a custom recovery (the correct one for your device) and took a backup with it before
you actually rooted the ROM then you could just restore that backup (any competent guide should tell you to make the backup before modifying the ROM, but it's amazing how many rooting guides fail to do this). Again that would remove root, but you'd still have your recovery so would have less to do if you wanted to try again.