Исправьте пожалуйста выделенные ошибки в тексте!

Исправьте пожалуйста выделенные ошибки в тексте! I think that is always better to have a teacher, because is very difficult to master the course material itself. If you have any questions or you do not understand a topic the teacher can only explain her. But it all depend on the skill of a teacher and the ability can explain it. If a teacher can not explain a topic that any help from you will not got. But some people who are well able to learn a material themselves and master his do not need a teacher. But without an explanation of material can not do. Now days the internet is able to replace teachers, because it contains all the necessary information. For example, video lessons, audio lessons , lecture material and other. But there are also all the teacher explains. So, this question is controversial for me, because I can learn from both alone and with the teacher.