You could ask a native speaker to record the tongue twisters for you (or maybe there are videos like that online) and repeat after them, comparing your pronunciation to theirs.

Yes, that sounds right. You're probably also going to hear things like "You'll be okay" or "It'll be okay".

I'd thought the word was "clearance" personally, but apparently "clearance" is simply getting rid of older goods to make way for new ones. (https://english.stackexchange.com/questions/97376/what-is-the-difference-between-clearance-and-sale) After doing a bit of searching, however, I found a close enough word. The sale of slightly damaged or scratched goods is called a "seconds sale".

So mad

I was so mad today. Well (using the word well seems a bit awkward) I am a photographer working for a hotel in Shanghai. For all the time Since I became a photographer here I have been using my own camera, which doesn't involved in isn't part of my working contract. Once I asked for them (managers) providing me a working camera their attitude wasn't clear. (rewritten) Once, I asked my managers to provide me a working camera, but their answer wasn't clear. I am so mad (you've been using the phrase "so mad" a lot. Maybe you could use "really mad" or "very mad" or even "frustrated".) because all the time I amusing have been using my own camera but I decided to let them know it's time to let them know what my value is. So I moved my camera back to my room and told them I would never use my camera again. After that they gave me a old camera from 10 years ago, which doesn't take better pictures than a smart phone nowadays!. (or you could say) The smartphones today take better pictures than that camera!

It would be more natural to say "A photo taken by me" or "A photo I took". However, since you're posting the picture and it seems like that will be the caption, it's more natural to just say "Taken by me". After all, the photo will be right up there; people will be able to tell that it's a photo.

You should continue speaking and practicing. You could also try translating sentences you speak in your native language into English. I'm... not from the UK and had to look up the various English levels, but it seems that it's a lot about the placements of the words and the naturalness of them. Watching various English movies and shows might help.

I think the most natural phrase would be "cause a scene". You could also say "make a racket" but that's more for disturbance by making loud noise.

If you want to improve your English grammar, you could keep asking for corrections on the italki website. You could also look up "English grammar exercises" and work on them. This is a resource I have used in school before, and the exercises should help to start you off. http://www.chompchomp.com/exercises.htm