TA struggling with how much time grading takes This semester I was assigned as a TA to a Class that I am not very familiar with.
As a result, grading takes me too much time.
For example, for a class of 74 people, it took me 24 hours to grade their assignments (7 exercises per person). One of the reasons it takes me that much time is that I have to study in order to refresh the content in my head before grading.

What should I do in order to make the procedure more time-efficient?
Should I tell my concerns to the professor I am TA for and as well as my PhD supervisor ? I fear I might seem lazy or unproductive.

To cope with workload whenever I have grading to do I make sure I finish it within one day so that I can focus on the other stuff I have to do in the next days of the week.

-----------------------Edit with answers to questions-----------------------

Since people asked more questions about my situation here are answers:
I keep office hours for 2 hours per week.
I have to grade 3 packages of these assignments for the whole semester.
The first package was for 91 people the second was for 74.
The was provided with indicative solutions but the answers are open-ended
One thing I might do in your shoes is to grade all the answers to the problems one at a time.

That is grade problem 1 on the assignment for all 74 students, then grade problem 2, and then add up the scores for the seven problems at the end.

That way, you can "prepare" for one problem, grade it on an "assembly line," and then forget about it after you go on to the next problem.