Explanation

 The use of "had been doing" in your sentence would indicate that the action of doing the kind of work occurred before another past event.

In this case, "had been doing" implies that the kind of work you were doing happened before the doctor knew you would recover.

This construction suggests a past continuous action that was ongoing up until a specified point in the past, which is why "had been doing" is used in this context.

Explanation

We generally use to with access. 

To is a preposition here.

Access to someone means کسی تک رسائی ہونا

Only the chief minister has access to the president صدر تک صرف وزیر اعلیٰ کی رسائی ہے

Explanation

Generally grateful is followed by to.

Grateful to someone means کسی انسان کا احسان مند ہونا

Grateful for something means کسی چیز کیلئے احسان مند ہونا

I am grateful to him میں اس کا شکر گزار ہوں۔

Explanation

I am having a party next week, but Pasha and Raheel cannot come

میں اگلے ہفتے پارٹی کر رہا ہوں، لیکن پاشا اور راحیل نہیں آ سکتے

Explanation

We should use By for certain time or date in Urdu meaning (تک)

Be here by 9 O`clock means نو بچے تک یہاں رہو

Explanation

By is a preposition here.

By shows a doer of an action

Invent means ایجاد کرنا

Explanation

Here committed means to be dedicated or devoted. 

Committed to means پر عزم ہونا

Pakistan is committed to that policy. 

Explanation

Be aware of something means کسی چیز سے باخبر یا آگاہ رہنا

I am aware of the problems.

She is aware of the issues.

Explanation

 We use preposition at to describe a position or location seen as a point.

At the end of the lesson.

Explanation

We generally use preposition By before transports like by bus, by car, by air etc.