Your response is quite clear, but there are a couple of minor corrections needed for clarity and grammar. Here’s the revised version:
Thaddeus Stevens believed that Andrew Johnson should be removed from office because Johnson failed to fulfill his duties as President. Stevens believed that Johnson had not obeyed the Constitution and had not correctly executed laws. Stevens also thought that if Johnson tried to avoid his duties, then he would be breaking his promise. Thaddeus Stevens believed that Andrew Johnson was not fulfilling his role as President and that he should be removed from office.
Corrections made:
- Changed "failed to his duties" to "failed to fulfill his duties."
- Capitalized "Constitution."
- Capitalized "President" in the last sentence to maintain consistency.
- Changed "the office" to "office" in the last sentence for clarity.
Everything else looks great!