meta has menu title not post title how to fix it?

i noticed in my joomla site does not set as title the titles of posts and keeps the title of the menu example
https://www.gyn.gr/forum-iatrikon-apantiseon/kentriki-forum/post/ponos-sto-nefro-prin-tin-periodo
<meta name="keywords" content="Πονος στο νεφρο πριν την περιοδο" />
<meta name="rights" content="Gyn.gr 2018" />
<meta name="description" content="Γεια σας! Ειμαι 22 ετων και εχω παρατηρησει σε μεγαλο χρονικο διαστημα,οτι περιπου 5 μερες πριν την περιοδο εχω εντονη ενοχληση στο νεφρο ανα τακτα χρονικα διασ" />
<meta name="generator" content="Joomla! - Open Source Content Management" />
<title>Κεντρική Forum</title> this should be what the description meta name is

bellow is an example of your page that works as it sould

<base href="https://stackideas.com/forums/request-for-help-rate-our-support";/>
<meta http-equiv="content-type" content="text/html; charset=utf-8"/>
<meta name="keywords" content="Request For Help: Rate our support"/>
<meta name="description" content="Hey guys, I believe most of you had already been experiencing the true awesomeness from our support team. Although we are not perfect, we strive to provide the best support that you can find anywhere else. To ensure that our support team is also delivering the same quality of support at it's highest standard, I would like to get some help from you ..."/>
<meta name="generator" content="Joomla! - Open Source Content Management"/>
<title>Request For Help: Rate our support</title>

why my joomla forces the <title>Κεντρική Forum</title> wich is the title of my menu....what did i do wrong can you please help me on that?