The completed sentence can be written as, "It's because you work too much" and "Well at least I finished that report now, so I can rest"
2. Someone left the ladder outside, look.
I expect that's Mike, he cleans the windows.
3. I work in the garden.
You did a good job
4. I heard that you and Harriet are building a garage
How long have you done that?
We have done about half of it
How to explain
The completed sentences contain examples of the Present Perfect Simple and the Present Perfect Continuous forms.
"It's because you work too much" uses the Present Perfect Simple. This form indicates a habitual or repeated action over a period leading up to the present. In this context, it suggests an ongoing pattern of excessive work leading to a particular consequence.
"Well, at least I finished that report now, so I can rest" uses the Present Perfect Simple. It emphasizes the completion of an action ("finished that report") that has relevance to the present, allowing for relaxation now that the task is done.