A form in html doesn't work real well

Hello, everyone,
I’m new in learning language php and have some trouble adjusting with html. and recetly I just have this little problem with the value when it sens to SQL, when I chose ‘other’ and tape something in the text, it always shows value ‘on’ in SQL, even if I’ve never written it in any of my scripts. It has been driven me crazy, I’ve tried everything about 3 days, please help me, thanks for your help in advance.
Due to the limit of the file I can send, i show you the form and a part of my code

I thought problem is probably here.