Sir is there certificate on kotlin language
No, as the kotlin course is created by community, not by sololearn so unfortunately there is no certificate for it.
U can learn basics form this site. https://codelabs.developers.google.com/
But there should be the certificate for it.
The certificates are not worth a penny anyway so. . . . .
Actually I am doing the course of android app development so I am also learning kotlin meanwhile I thought to get the certificate too