Merhabalar...I´d like to know when to -dir and when to use -den beri....Is there any specefic rule?Thank you very much

If you use the search box at the top right of this page you will find lots of previous posts covering this topic, with example sentences.

...../den beri (since) is used where the action is still continuing (iyor)

....dir is used for a specific period (X hours/days/weeks/months/years)

Has any foreigners heard the word "dırdır". I always remember this word when I read something about -dır suffix

Honestly I wanted to do so, but I don´t know whow I forgot Anyway thank you...Still my question is that in some cases we can use both -dir and -den beri, can´t we?

Quoting GulBahar

Honestly I wanted to do so, but I don´t know whow I forgot Anyway thank you...Still my question is that in some cases we can use both -dir and -den beri, can´t we?

Think "dir" as "for" and "den beri" as "since". Most of the time you can use "den beri" instead of "dir"

From now on you will remember that grave stone!

(Elbaki, Merhum ve ğafur ila rahmete rabbihilğafur)
Karı dırdırından vefat eden Esseyid Halil Ağa´nın ruhuna fatiha

Sene: 1260 (1844)

Location: Merkez efendi mezarlığı, Istanbul (Merkez efendi cemetery)