_FieldCaption_Interests_Join

on the join page i have this "_FieldCaption_Interests_Join" , I reckon it should be "interests"

how can i get change it??

That is a language key.  the prefix tells you it is a caption for a field.  Go to your admin, settings, language settings.  Copy the key into the filter box and click the checkbox.

You can then enter the text for the caption.

 As GG said, that looks like a missing language key that should be there on a default site. (It shouldn't have to be added as it is a default key.)

How did you install your site?

 @gg :

 I did that but it didn't change 

 softaculous ?

I tried what gg told me, but it didn't help!

i fixed it 

i had to add a key to system 

Cheers guys!
 

I should have added that part.  If you create a new field, it will add the language key to the field parameters but you have to manually create the language key as well.