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This sentence is correct if someone took the photos of you - have sth done

'I am very happy today because I took many beautiful photos.'

This is correct if you  took the photos.

Remember that 'I' before a verb in English is always a capital (big) 'I' even if it isn't had the beginning of a sentence.

Best wishes

Bob

the first

Notice:1. "I" should be capitalized.

              2. It is "beautiful".

              3.  "had done something" means you already made it. But here, I recommend you "I took many photos".

              4. The letter “s” terminates most plural nouns.

Good luck!

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You did