My dear sister,
Islam is not the religion of opression.
You can talk,have jokes and be friends with a na mahram.It is allowed unless with a bad intention like sexual lust e.t.c
Imam Khamenei even said that if you want to marry someone you can look at her beauties like hair,foot,face,hand and other beauties without intention of lust,even if lust arises undesirely,but is to be made sure that you don’t know that they will reject your proposal.
See the exact statement by his website:
To Look at Her Beauties for Marriage A person, who wants to marry a woman and for getting