I’m not very tech savvy, apologes for a stupid question.
I want to design the front page of my website with Webflow amd point at www.mydomain.com
But I need to have Wordpress on a subdomain like blog.mydomain.com
Is it gonna be a problem or not?
Thank you kind people
Howdy @Did_Makov and welcome to the community! 
Not at all, just make sure your Wordpress site is setup to point to the “blog” subdomain in the DNS settings at your domain registrar and you should be good to go. Admittedly I stay away from dealing with Wordpress sites so I’m flying blind here, but it looks like you may also need to “add a mapping subscription” (outlined in the link below).
Each registrar is setup a bit differently so the DNS update process may vary from place to place, but here’s a Wordpress tutorial I found that should get you going: