How should the instructors and learners deal with the use of L1 language in a L2 classroom?

1. Research question: (this should be formulated as a ?question?, not a topic.)
How should the instructors and learners deal with the use of L1 language in a L2 classroom?

2. Research method: (e.g. quantitative and/or qualitative)
Both quantitative and qualitative

3. Data collection tools: (e.g. experiments, questionnaires, observations and/or interviews) + (how many?)
Questionnaires and interviews. I will try 40+ student participants from different levels in a preparatory year program, and 10+ instructors (Those that speak Arabic and non-Arabic speaking).

4. Statistical analyses applicable (if any):