You can retake the both exams at once during on the official retake date - 06/07/18.
You cannot keep only a part of the retake grade. If you retake the exam, its entire grade will be used as 50% of your course grade.
You cannot retake the assignments.
If you want to get the best possible grade, treat the deadline for assignments as strict.
A day ends at 23:59:59. If your submission is a second late, it is a day late.
You still receive a grade for a late assignment, but for every extra day you lose 20% of the grade. Hence, after the late day #5 there is no point in submitting. Any assignment submitted later will not be graded.