Good evening Antonios and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
As a first step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Secondly, it looks like the WordPress theme (Avada) you are using has some template customizations going on for the single-event view.
More specifically, the ticket form (from tribe_events_single_event_after_the_meta) is part of the 2 sidebar templates of Avada.
You can find them in Avada > Templates
This is probably a question better suited for the good folks at Avada, but you would need to do a child theme where you remove that call from the sidebar and add it under the events content in Avada/tribe-events/single-event.php
You might want to read our Themer’s guide to get a sense of how that works.
Let me know if that helps.
Have a great day!
Geoff B.