That actually looks quite typical of what happens when you install the beta patch on top of the last beta without making sure CoD is in a "clean" state.
I´ll post these steps once more, follow them machoo and see if you still have the texture bug (wont solve the blue stripes sadly enough though
1) Open steam, go to library, right click Cliffs of Dover, Select Properties and go to Local Files tab, click on Verify Integrity of Game Cache and let it run and download.
2) Go to \Documents\1C SoftClub\il-2 sturmovik cliffs of dover\cache\ and delete everything in the main folder, keep the shaders folder but delete everything inside.
3) Delete your conf.ini in \Documents\1C SoftClub\il-2 sturmovik cliffs of dover\ It will make a new one next time you start up the game, you have to set your video settings again first time you start the game.
4) Download the latest patch and extract it to your desktop, then cut and paste all folders to \Program Files (x86)\Steam\steamapps\common\il-2 sturmovik cliffs of dover\ selecting yes on any request to overwrite and copy and replace otherwise.
5) For ATI users go to C:\Program Files (x86)\Steam\steamapps\common\il-2 sturmovik cliffs of dover\parts\core\GUI\ and rename the intro.wmv to something different or just delete it, just be careful as it might affect VAC cheat protection in the future when playing online, so far there seems to be no problem to do this though.