~ と思います
1. No particle after てんき?
2. つぎ
のテスト. Also, recheck how to end a sentence in the plain form with an い-adjective.
3. They're just going to listen to karaoke? Grammatically valid, but seems like a strange thing to do
~といっていました
1. Where did the も go?
3. Where did the わたし come from? This makes it possible to misinterpret the sentence as Mary saying that *you* live in 京都. Oh, and make sure to keep the tense of すむ.
じょうず/へた
2. Video games <> テニス
3. Needs a nomalizer の. In 5) you did write it though.
4. Best rewritten as 日本語ではなすのがじょうず or just 日本語がじょうず like in 1)