What should I do in a tough sparring session?

I’ve been doing Muay Thai for two months, but before that I did K1 kickboxing for two months. In total, I’ve been training for four months. I’m 1.80 meters tall and weigh 100 kg. At the Muay Thai club, we spar, but it has to be relaxed. Some of my training partners, around 1.70 meters tall, sometimes hit a little harder than normal or throw uppercuts to the face. What should I do in that case? What I like to do most is throw teep and middle kicks, as well as internal and external low kicks. Should I hit them a little harder too? I only touch them with teep kicks. I’m afraid to hit them with any real force; I think I might hurt them or send them flying. But at the same time, I don’t like how arrogant they are. Currently, this only happens with two people at the club; everyone else just spars lightly.