Он помогал – is never translated in perfect simple Он помог – is never translated in progressive tenses So, when your situation requires past progressive or present/past perfect progressive – say 'помогал' when you need present/past perfect in English – say 'помог' in Russian sentence and about Past Simple: Он помогал – he took part in assistance or aid, once or many times Он помог - the problem is solved and he helped Be careful: Он помогал делать (оба глагола несовершенного вида) Он помог сделать (оба глагола совершенного вида) However, these verbs may often be interchangeable I hope I could help.

Он помогал = "He was helping". The action in progress. Он помог = "He helped". (or "He has helped", depends on context) The action is complete.

"Он помогал" also can mean a repetative (regular) action in the past. The difference will be clearer if you read about the perfective and the imperfective verb aspect in Russian.

Hi, dude! Nice to see you again! You pose really interesting questions, which means you have a very inquisitive mind! Well, simply put, in answer to your question, "помогал" implies a continuous action for a certain period of time (for instance, in English you'll say "he used to help me" in this case), while "помог" implies a one-time action (for instance, "he helped me just THIS once") and lacks any continuity. Hope I helped! See you! Keep it up, you're doing a really good job at studying Russian!