English to Latin translation help please.

[lachlan]

i was wondering if someone could "check" my translations and let me know if im doing them right.
id really appreciate it.

-Your new friend was writing a letter to my sister.
Tuus novus amicus scribebat litteras as mei sorori

-Nevertheless, the author of the book will teach my brother to write beautiful literature
Tamen, scriptor libri decet meis fratris scribo pulchras litteras.

oh & I had another one that is latin to english ( i have no clue what audb
-Quare, scriptor littereas de insidiis scribere tum non audebat
Therefore, the author did not dare to compose the littereatures about treacheries then



thnx in advance.
Lachlan

[Swth\r]

[Adelheid]

-Nevertheless, the author of the book will teach my brother to write beautiful literature
Tamen, scriptor libri docebit/instituet meum fratrum scribere pulchras litteras.

I would say ' fratrem' instead of ' fratrum', if you meant this to be an accusative singular. Not even sure if that should be an accusative and not a dative.

[spiphany]

-Your new friend was writing a letter to my sister.
Tuus novus amicus scribebat litteras as mei sorori

"sister" should be in the dative without a preposition (indirect object, no motion involved)