USB stick is made in Rufus (choose GPT for UEFI -option). Secure boot is off. From now on I don't know how to continue :/ . I'd so much like to wipe Windows out. Installing is no problem. Boot loader is... or I just have no clue ;D. More chewing gum and black coffee!
The screen keeps flickering when using Ubuntu on Acer. I guess downgrading to 14.10 or 14.04 might help? However no extra drivers were needed. Touch screen worked out-of-the-box! Downside is there was neither wifi nor sound.