I do agree with Mr.Lance. I am a native English speaker (USA) and not a teacher. I would say "in the front of" implies that you are in the VERY FRONT. I am in the front of the line (queue). In the US we use the word line and not queue. In Britain I believe they would use the word queue. You could also say "I am in the front of the store". That implies you are located at the front of the store, perhaps by the entrance doors. Just to clarify in this last sentence you could also say "I am AT the front of the store. Both would be correct. For that matter you could also say "I am AT the very front of the line." and it would be correct also. The term "in front of" is a very general description of your position. You could be "in front of your friend". You may be behind many other people and also in front of many other people. Using these same terms in another sentence you could be "in the front of the car". This means that you are in the front seat of the car. Not the back seat of the car. In English would would say "I am in the front seat of the car." Without putting the word "seat" it would not sound right but the sentence would be accurate. Same car example but use "in front of". I would state that "I am in front of the car". What this would imply is that I am actually standing in front of the car but I am on the outside of the car. Unlike the previous phrase in English you could use the sentence "I am in front of the car" and it would be correct. Most likely I would say "I am standing in front of the car". Prepositional phrases are very difficult in any language. For example, I would say "I am on the internet" or "I am on the phone". Clearly I am not lying on top of the internet or phone. But the word "on" implies something on top of something else perhaps covering it up. A bit off topic but hope it is helpful. BTW (by the way) great question.