Dear student,

Please note there are many apps that offer such courses. You can joint them if you like but I would suggest you to check if their teaching is compatible with you. Are you gaining the required information you need, whether you are understanding what is being thought, and their response towards your queries. All teachers have a different level of teaching. So I would suggest you if it's helping you alot go for it. If not please leave don't waste your time.

All the very best I wish you good luck with your studies.