I have to disagree the first couple comments, "7-8 hours wasted daily" certainly does not sound normal. The amount of time is not necessarily an issue, but it is far longer than I ever spent on homework and if you feel that you are being inefficient you're most likely correct. It sounds to me like you are indeed getting bogged down in unnecessary things or (perhaps more likely) just struggling to piece all the little things together into the big picture.
A big part of higher education is learning how to learn efficiently. In your career and in life, this will most likely be much more useful than the actual material you cover in your courses.
I think there are a few things you can do that might help:
- When reading a textbook focus on items that are formatted in a way that stands out. Textbook authors format material to emphasize critical and major points. A good lecturer will also make an effort to highlight the big picture topics and build up the details around them.
- You might try studying or reviewing notes with a classmate before starting homework assignments. Ask for their insights on what the most important things are and try to formulate your own judgments as well.
- Visit office hours. Ask conceptual questions about the topic at hand. You might also consider explaining to the TA or professor that you're having a hard time picking out the crucial material from the details and ask if they can help you focus in on the key topics.
It has been my experience that many students get bogged down in peripheral details when learning new topics, not seeing the forest for the trees. It has always helped me to ask myself what the most critical concepts are and then be sure to understand the details as they support these concepts. Hopefully, with practice, you will soon improve at picking out the key concepts and building a mental framework around them rather than getting bogged down in all the details from the start.