Is HelloTalk free?

I'm curious to know if HelloTalk is a free service or if there are any costs associated with using it. I've heard great things about the platform for language learning and I'm interested in trying it out, but I'd like to know if I need to budget for it. Can you clarify if HelloTalk is free to use, or if there are any hidden fees that I should be aware of? Additionally, are there any premium features that require payment, and if so, what are they and how do they enhance the user experience?