Hi, when I send a topic link through whatsapp or telegram, user open the link and find the sign up option, after the sign up is finished here is the issue poin, the page opened is not the original link shared, after click on validate email link the user can not see what originallly receive, the page is return to website homepage...Is possible:

After the email is validated return to the link page which received.

When a user click on a link, maybe user need to sign in, but after sign in recognize and return to the link page received?

This is not something in which is possible at the present time, unfortunately. The validation link will always lead to the validation page, which in turn leads back to the main page of your site once validated. If they then click the link and log in, it will of course lead them to the correct location