I am going to explain, but i will not give the answer. If you are still stuck after this, please let me know and repost your code, i will help you further.
I am going step by step on the previous exercises, starting at exercise 5/15 and assuming you are stuck at 7/15. In this exercise you need to add two table cells with the values 1897 and 1935, which result in:
<td>Bride of Frankenstein</td>
now, in exercise 6/15 you are asked to add
<tbody></tbody> tags. everything in your table should be inside the table body cells, so add a tbody opening tag after the table opening tag, and the tbody closing tag before the table closing tag. The exercises says they already create the table head tags for you. I would (given the fact that your code is quit a mess) add them to the code you have now, add the thead tags between the table opening tag and the tbody opening tag. Now you can follow the instructions from the exercise