I think it works, but it depends on what you're hoping to get out of it. The problem is that a machine won't correct the systematic mistakes you keep making, you know? Like, it can tell you "that's wrong," but it doesn't understand why you specifically keep falling into that error over and over. Plus, a real conversation has rhythm, interruptions, background noise, people talking fast... you don't get any of that the same way with a chat.
That said, for breaking the ice and getting over the embarrassment of speaking, it's pretty good. If you've been at it for 3 months and you're starting to feel more comfortable, that's already something. Plenty of people screw it up by not practicing at all, so you're doing more than most. The ideal would be to combine this with something else: watch series in English, listen to podcasts, YouTube videos... stuff where you hear real native speakers, not perfect AI responses.
If you can afford a teacher, cool, but it's not essential if you're disciplined. A teacher speeds things up and breaks your bad habits, that's for sure. But if right now you push through with the free stuff, actually practice several times a week, and mix it up (not just chatting), in a couple of months you'll notice a pretty decent change.