Scrum is good at time management because it puts every activity under track without any exceptions.
All what you are doing should be tasks on the white board.
Requirement analysis, tech design are now grooming sessions and spikes. They are all scrum terms and will be handled in a formal way so time spent on them will always be calculated in your plan.
You don’t have to have a big grooming session to analyse all the user stories for next sprint. That will be tiresome since it takes long, and people won’t like it.
Instead you can break them into small ones, like a one-hour session everyday for a few days while you are still going on current sprint. During every session, you still try to clarify the user story as in detail as possible and work out a design and task break down on spot if possible.