I made some orders. Can I send these works to others as an example?
Your buyers will own the rights to them (unless you specified otherwise in your gig), so not unless you get their permission first.
As @uk1000 has rightly said, your clients own rights to whatever job you do for them…some would even make you sign a DND agreement before working with you. So… do not send a client’s work to another as a sample.
Welcome to the hood, have a good freelancing time.