When editing page (forum page created via ACP) and save changes, changes are not visible on forum page, but in ACP shows that I have outdated template (that page). If I click on save changes, it saved but changes are still not visible cause it not saved at all.
I have to go directly to template and if I make change there and save, it saved OK and shows change.
Changes made to the "Template HTML" field of the Edit Page page of the Admin CP will be applying changes to the Master version of the template. Editing the page node template via the template editor will, by default, be editing your default style.
With this in mind, I would recommend editing the template directly, rather than attempting to edit it via the Edit Page page. The template editor there is more advanced anyway.