Translation of menial in Spanish

I usually charge 15 dollars per hour, but I don't care very much for the hourly system. I can also help with corrections and suggestions, but only if the original text is a serious translation and not an automatic one.
Everything in your letter is perfect! Almost no errors and the writing style, very impressive! After this first year in England, you have also improved your vocabulary and the grammar skills.
What is the past tense of 'to swim'? So either you say, I was swimming or yesterday I was swimming. Or: I was running yesterday vs. yesterday, I ran. You know the answer? I have no clue.