An English class in Spanish

After a demo class in mandarin performed by one of my instructors for a bilingual class where none of them speak the target language or understand it. Consequently seeing their reaction, interest on the class, and participation I have come the conclusion that I have been failing as an English instructor, but the good thing of all this disappointment is that is never late to start doing it right.
I have always had the impression that I needed to provide instructions in L1 for EFL student to understand and then continue any activity, also I used to translate vocabulary words or phrases instead to try in TL all the time, for them to get familiar with the new language and start thinking in the new language with a translation attach to it.
I have to create a strategy for this because I know it won't be easy for me, I will have to change my own way of teaching first and avoid to all cost L1, then think on a suitable method for the lesson to provide introductions or warm up, as well as the lesson itself in the TL.
Unfortunately, I thought that was almost impossible to give a complete lesson in the TL, for that reason, I'm so glad my instructor did this activity to shows us the level of comprehension that could be achieved, as well as participation.
I know it will be a long way to change my current methodology, and way of thinking, but I already started by knowing that it's possible to be done.