This paper deals with a course of mathematics at an university in the Czech Republic. This course is for incoming students. It prepares students for math entrance exams. During the coronavirus pandemic period (2020-2021) we taught the course online. We had to solve the problem with communication with students and obtain feedback from them. For this reason, we used interactive quizzes. In this article, we compare the situation at other universities, and we introduce online quizzes. Further, we compare their success rate during the course. In addition, we present the results from the student´s course evaluation survey.