How to find the right balance between details and the main ideas?
In mathematics, being able to read papers is a skill on its own, and learning how to do it properly is part of “mathematical maturity."  Most everyone runs into this sort of problem at first, and with practice, you get better at seeing the forest through the trees.

One concrete strategy is to skip the small steps and to assume the details in them are true.  You can verify those details after you understand the main ideas.  Of course, you still need the skill of telling apart the small details from the important ideas.  Same goes for research -- you can make a big plan of attack and assume the details will work out later, and then if the big plan succeeds, you can go back and do the detailed calculations carefully.  Here, what is needed is intuition about what "should be true if worked out."  But such intuitions take time and practice to develop.