Hi Hiromi! You can use iTalki without buying lessons, for sure. You should take a look at the menus at the top of the website to find all the different features out here.
Here are the top features in my opinion (if you're not planning to buy lessons):
- Community - Answers: You can get an answer to your question on e.g. grammar, or a sentence that you have trouble understanding
- Community - Notebook: You can write a whole blog post/letter here in foreign language, and people who are proficient in the language can give you a translation and tips on how to fix them.
- Community - Language partners: This is important if you want to practice spoken language. Scroll the list and find people who are willing to be language exchange partners (i.e. wanting to learn Japanese, willing to help you learn English). You can send them a message if you are interested in contacting them.
- Community - Discussions: For talking about anything you are interested in, it can be a comment, opinion etc.
Personally I study languages using phone apps (Duolingo etc.), reading books in foreign languages, watching TV, reading grammar books, listening to foreign radio/podcasts and also using the features I listed above -- there are more ways to learn than I have time to dedicate for studying.
I don't need to learn any languages, I just like to learn them, so I tend to choose learning methods that are perhaps more fun than they are useful. :)
Hope this helps!