Someone already mentioned this earlier, but I will repeat it because it stuck out to me when I read it also. I think your first reading was correct and I would find an instructor whose first language is the same as your own to go through the directions with you. Possibly contact the computer co and ask if they have the directions in your native language.
I think this makes sense and as a fellow warm water vacation diver with limited experience, I can relate to a certain degree. One piece that is very valuable about the various models is what Devon described as the 'red flags' written into the RGBM. If your NDLs seem low compared to fellow dive buddies (as was the case in the dive you describe) use that as a signal that some of your dive technique was flawed that day/week. Ask your dive buddies to take mental note of your buoyancy and trim and give you feedback later- or even in the water during the dive with some predetermined signals.
I say, stay focused on your choices that not only led you into deco, but led you to 35 mins of deco when you had the opportunity to have only 7. There is no reason to believe that getting a different computer or diving nitrox will do any good until you learn the actual lessons of this dive, which are that you ignored your computer when it was telling you precisely what to do.
It does not appear as if you communicated with your buddies that you needed to end the dive and that you had a deco obligation. (If you did communicate with them and at least one of them wouldn't end their own dive to ascend with you, find new biddies) I recommend developing some signals with them that allow you to communicate your general NDL situation. The buddies I dive with and I keep it really simple. We'll make circles around our computer with our index finger and do a thumbs up. Often we follow that up with a signal that means, "I plan to go up a little." (thumb and index finger abut an inch or two apart) If we are below 10 mins of NDL, we flash the number of NDL mins we have. As a buddy, I now have awareness that I need to go up with my buddy, why they want to ascend to a shallower depth, and that we may need end the dive if the NDLs don't increase enough to their liking.
I also recommend debriefing your experience with your dive buddies from this trip. If they are not uncomfortable with the DM's response to the deco time you had remaining once back on the boat, then find other buddies. Seriously. Having someone else clear your computer for you is beyond irresponsible.
Last, make sure you know how to use the "plan" mode on your computer if it has one. Some even allow you to enter a hypothetical SI into it, so you can plan a dive based on a specific SI. This allows you to see how much of an SI you want so you can do the next dive you want to do. I will often communicate this to my buddy, too.
I commend you for sharing your story on SB and I know I have learned a lot from this thread. Thank you for posting.
