Grammar-wise the sentences are fine... but there are several other issues you might want to consider. Word choice - one usually doesn't
respond to an advertisement. Next, two times
your is redundant - would a third party post a job offering on their website? Possible, but unlikely. Also, I would follow Araucaria's advice about sentence order. Verbs like 'I read', 'I am writing' etc are fine but they can make your letter bulky and deflect reader's attention from other important things, such as you qualifications and achievements, if this is a motivation letter for instance. —
Lucky 2 hours ago