This is a pretty old series of lectures by Marianne Talbot, Critical Reasoning for Beginners. And there is a newer series Critical Reasoning: A Romp Through the Foothills of Logic.
The first course is six hours and forty five minutes long. It is a course for beginners, most likely you don’t need any critical thinking training to watch it. As the videos are recordings from lectures, you can hear some questions from the audience. It may slow you down a bit, but it may also help finding answers to questions you may have. Text on the slides in the videos may be hard to read, but you can download these slides separately. The course is pretty short, you can even try to watch a lecture or two to decide for yourself do you need it or not.
The first course covers the following topics: the nature of arguments, different types of arguments, identifying and analysing arguments, validity and truth, evaluating arguments. It isn’t a complete critical thinking course, but it still can teach us some relevant skills. You can also use this course to better understand how logic is used in creating and understanding arguments. You don’t need to do any homework, but you can apply methods from this course to analyse different texts to find some logical structures in them.
The second course expands topics from the first one, so it can be used to gather more knowledge on argumentation and critical reasoning. You can also repeat several topics to remember them better. Here is the list: recognising arguments, identifying premises and conclusions, classifying arguments, evaluating deductive and inductive arguments, errors in argumentation.
The second course has answers to questions the author asks during lectures. You can answer them then check yourself. It is a bit longer than the first one, nine hours and five minutes. Still even both courses combined together are pretty short comparing to other online courses. But you may need some additional time when you start applying knowledge from the course to real life arguments around you.
I can recommend to try these courses if you want to improve your understating of arguments. Analysing arguments may take some time, but it may help to check the validity of different sources of information. Please also have in mind that these courses represent only a part of critical thinking skill set, but this part is useful on its own.