Issue creating a Multilingual Website.

Hello,
I am facing an issue trying to translate the contact form of my website, with the Transposh plugin. Particularly the “Submit” button at the end of the contact form can’t be translated. As you can see here https://www.coho.gr/home/en/contactus/

After talking with the plugin author he replies to me saying
“ Buttons with the value attribute can’t be translated as this attribute might be used in the processing of the form,
If you wish to translate it, you may either use gettext or the transposh_echo() function inside your code “

My question is how can I solve this problem as I am not so familiar with php or gettext? I am thinking to buy wpml and gravity forms just to solve this issue, but again I am not sure if this is going to work.

Thank you very much ??
Have a nice day!
Best Regards,
Dreamguard