Few different options come to mind (there may be more). Many people have a sensitivity to PG which is an ingredient in most liquids. The coil or heating element could be bad which can give harsh hits. Nicotine is the biggest factor on how 'harsh' a vape seems. I am bias against starter kits such as haus. I started with something similar as did most and while many people use and like those type devices In my experience they cause more problems. My point in that rant is not to sound like a tool but to say IMO the
tank/ thingy holding the liquid may just be of poor quality. Air flow can be another issue. Poor air flow can lead to a harsh vape for sure. So for trouble shooting I'd suggest trying a lower nic first, new coil second. If you lower the PG and increase the VG ( the other main ingredient) it may not wet the wick fast enough and burn the coil. VG is thick, PG is thinner, and factory made coils often times struggle with the high VG.