halfbike pulls to the right

hello all, i bought a second hand halfbike which i guess wasnt much in use. nevertheless it keeps pulling to the right. i always have to work against it which doesnt make it easyer to ride. it took me a while to be sure about this fact, because in the beginning i was very insecure riding the bike. but yes, after some days i`m doing quite fine and i`m sure - this is not okay and its definitely killing some of the joy. i already wrote to the support some dys ago but have no answer yet. would be very graetful for some tips!! thank you : )