- It's grammar.
- It's preposition.
- Start every sentence with a capital letter.
- End every sentence with a single punctuation mark.
- Put a space after a full stop, comma, question mark or exclamation mark.
Please don't put words in such pale colours as that bright green. They're almost impossible to read. I don't know why you specifically put the prepositions in that colour, although I realise you were querying their use. I have marked in red every word that has some kind of error, either with capitalisation, spelling, punctuation or grammar.