Try reading this ~ How to participate in events [Guide]

General - Automatically given to players upon registering to forum.
Advanced - Given to players who have been forum members for at least 30 days and also reached 100 posts.
For more info, check this ~ Forum

From what you describe, you might have seen either a hacker or a lagger. If you ever see something like this again, you can record a video and report it over here.

All of the players in the group must be not more than 5 ranks above or below the group’s creator's rank.
For more info, check ~ Matchmaking System

This was the case in the past, everything changed after the Paint Separation Update. As for now, paints are cosmetic items and they grant no advantage.
Here are a few helpful pages you might want to read;
Modules Paints Micro-upgrades of Modules

You should get your promocode within 48 hours. In case 48 hours passed and you still haven't received your promocode you should contact @SuperNick95 or @The.L-E-G-E-N-D via Forum PM.

As far as I know it doesn't have full immunity. 
Here's a great video made by the RU content helpers showcasing the new hull augments (skip to 1:20 for Stun Immunity); Update #599 - (Released 24th April 2020)

You need to have Railgun & Hornet/Wasp MK7 in order to play XP/BP. I would recommend you to create a battle with no format and name it "XP" 
For more info, check ~ Format Battles

This issue has been reported, meanwhile you can try clearing your cache. ~ How to clean Tanki Online clients cache?

It depends on when the next eSports tournament will take place, the closest tournament is "Blitz N10.20 | Hard" which should start in 2 days. I guess there should be a live stream.

I am pretty sure the map with the most Gold boxes zones is Stadium with 51 drop zones.

Kindly check this article ~  Server connection closed

The following article could be helpful ~ "Server connection closed"

Follow the steps in this guide if you use the client, or use this guide if you play via your browser

I would recommend you to ignore the player by pressing on his/her nickname and then ignore . This way you'll never see his/her messages again.

Try filling this form.

Hey, these articles might help you out;
How to raise FPS on the new HTML5 version
How do I raise my FPS?

In order to play in eSports, you need to either join a clan or play in a tournament that is open to everyone. I'd recommend you checking the following pages ~ How to join a clan? & How to participate?
For more eSports related questions use this topic ~ eSports Questions & Answers