selam arkadaşlar

can I say

herşey yolundadır = everything is ok

teşekkür ederim

Yes you can. It means literally "Everything is on its own way."

Most of the time we don´t use "dır" at the end of the predicate. "dır" can also give such a meaning that you guess something. So if you don´t guess, there is no need to use "dır". But if you use it, it is not wrong but unnecessary here. So "Herşey yolunda" is better.