Hello atanas, this is wordpress, even though we provide development services for a price the community is amazing and you should always be able to find someone that can help you out.
What you want to do is:
1) Update to the latest Contact Form 7
2) Use FTP to access the file scripts.js (in the contact form folder under plugins): wp-content/plugins/contact-form-7
3) go to line 87ish: if (1 == data.mailSent)
4) Add
location.href="https://www.URL.com/new-page/";
5) Change URL to your ure, and new-page to your page or page.htm /php etc
6) This should go right under ro.addClass('wpcf7-mail-sent-ok');(about 2-4 lines down from data.mailSent
7) Save
And you should be ready to re-direct on successful submit.
