how to include a contact form

I’ve tried to include a php conctact form with a simple php include command on the contact page, however when one now clicks on the contact in the menue the form gets displayed in the browser all by itself but not as part of the page.

I’ve tried several approaches but always get the same result.

I’ve searched for answers but only found the form plug in which looks to me too technical to handle.

Is there a simpler solution?

Thank you.
best regards,
Glenny