In my opinion, there are 2 things you can do.

1) talk to the mirror

2) talk to a language partner or an affordable tutor

By talking to yourself, you can practice your toungue. Speaking the new language out loud is incredibly helpful. You need to start off really slow. After 20-30 reps saying the same thing, you will see the difference. This was how I practiced speaking English every day.

It is inevitable to find a real partner/tutor to pinpoint the mistakes you have. This way you can learn in a faster pace. I have tried both. For language partner, it might take 2 hours every time and it might not be productive sometimes. Some people speak the language naturally but don't know why and are not very keen to correct you. I now prefer having a teacher. Learning a language doesn't happen overnight. My advice is to find affordable teachers and let them practice with you every day for 1 hour. It will be very productive.

I have tried a language marathon/sprint from another platform to learn English for 90 days non-stop. It wasn't very good in my opinion because they were group lessons. I now created my own approach. I have 5 English teachers who charge me only $10US/hour (you can adjust whatever affordable for you). My English improvement has been furious because now I can write this long comment and you can understand me so far.

Good luck on your journey.

找一部自己喜欢的中国电视剧，在里面跟读自己喜欢的角色。

The best, ideal way would be having conversations with someone, but of course it's not always possible, which is why it's so difficult to self-learn.

But perhaps you could try to have a conversation with yourself? Learn a few question structures and try to answer them. Ask yourself what you ate this morning and answer it in Cantonese. You can even write a script and read it out loud!

I can communicate online these days