The construction worker carefully put the finishing brick piece to complete the building project. OR, in another sense of "put": "He decided to put his answer in the most diplomatic way he could."
No, you cannot. The word "their" means "belonging to them." You are thinking of THERE IS, which can be put into a sentence. There is a good reason you need to learn grammar. There is much less chance...
An angry bird scratched my arm! "An" is usually put it a sentence to tell you the noun next to it is singular. Usually if the noun starts with a vowel (A, E, I, O, U) you use "an" if not you use "a"....