Translation:I have washed the car today.
Can this not also translate as "I washed the car today"?
That's simple past rather than present perfect and would fit better with the Welsh simple past.
Today I have washed the car?
What is the full form of the contracted " 'r " and what does it mean?
yr means "the".
It takes one of the forms 'r, yr, y depending on the surrounding sounds.