Then they cannot prove you are the account owner, you need to go for a different approach now. You should respond back to the message they sent you, and this time repeat your information to them. DO NOT POST anything on the forum, as this is a game offence and will lead to a permanent account blockage.
This is the format they would like the information in:
1. What's your nickname?
2. Have you ever bought any in-game items or currencies using real money? If so, please specify the dates, payment methods, and the purchased items' names. Please also attach any receipts or extracts from the payment history of your bank account or virtual purse.
3. When did you register the account? Try to specify the approximate date.
4. Which email address was firstly your account linked to after the registration?
5. Which severe bans/punishments were on your account?
6. The last time you entered the game (date)?
7. Where do you play from (country, region, city)? Please provide a screenshot containing your external IP address from the page http://whatismyipaddress.com and place it on a free image hosting website such as https://imgbb.com/
8. Have you ever changed the nickname on the account? If yes, please tell us your first nickname and history of renamings.
9. Did you contact us before regarding this account? If so, we would like to know the email you used to do it and the essence of the request.
10. Tell us whether you have a Facebook or VK page linked to your account. Would you please send us the link to your profile ID?
This article will help you to find the Facebook ID https://www.facebook.com/help/1397933243846983/?helpref=related

You can find information on how to make a screenshot and upload it here: https://en.tankiwiki.com/How_to_take_a_screenshot
After this, you will be asked to press a getuserip link. Please do not press it with a VPN or anything, but your real IP/device that played on the account. Please make sure you give your answers in detail to Tanki Support. If you cannot remember your information, you need to clearly state why you cannot remember or try to guess it approximately. If you cannot, do not state an answer as it will mislead the support and they will refuse your request. Other than that no one can help you to return your account, until you can prove you are indeed the owner. I would suggest providing them your password (make sure the recipient is help@tankionline.com, they should have responded to you already), as the account has 2FA it should be safe. They will see that you most likely are the owner, and do their due diligence.

What you are describing, seems to be more of a bug in certain textures. This is quite common throughout many maps in the game, and you can't really fix it but use your knowledge for your advantage. If you provide a video, I can investigate it for you, but most likely this is a texture bug. I call them "hard" or "soft" surfaces, where soft surfaces won't allow the projectile to ricochet off and hard surfaces will. This could be an intentional or unintentional game design; I further remember this was also the case in Flash times as well.
All hulls have different dimensions in this game, and all objects in the game have a unique id unless they are duplicates. This is further affected by the physics of the map, and mode that it is in. For example, Space mode or Cosmos mode, will change the gravity and the way the tank interacts with objects as well as it's knockback and recoil on shooting and receiving shots. (This can also apply to the above question too).