[KyleGoetz]

Originally Posted by OzukakiBurasuki

I am now in Japan.
今、私が日本でいます。 or 今は私が日本でいます。 Or should I use 日本に instead of 日本で?

First off, there has been some heavy discussion about は vs が the past couple weeks on JF. It appears you have completely missed that discussion.

1. You need は not が
2. You need に not で: you do not use で with ある／いる; you use に

Ms. Tanaka is fine. Mr. Yamakawa is not fine. (I assume by fine they mean 大丈夫)
田中さんは大丈夫です。山川さんは大丈夫じゃありませ ん。 ?

A number of native speakers have, over the past year or two, pointed out that じゃありません sounds bad to their ears because you're mixing a casual じゃ with non-casual ありません. Either ではありません or じゃない. Here, ではありません since you've used です already.

I went to the mountain with a Japanese man and woman.
私は日本人の男の人と女の人で山に行きました。 (do I need to classify both as 日本人 or is it assumed?)

You should use 男性 and 女性, not 男／女. Also, you only need 日本人 once. Also, if you go with someone, you と, not で. Using で here makes it sound like the people were tools you used to get to the mountain.

I ate dinner with my friend on Tuesday.
私は火曜日に友達と晩御飯で食べました。 (Would i need to put 火曜日に before 私は? Also does it sound okay?)

を, not で. Also, don't use the kanji for ご in ご飯. It looks weird. I know at least masaegu will back me up on that one.

On Wednesday, I drank a lot of alcohol. And then I saw a video.
私は水曜日にたくさんお酒を飲みました。それから、ビ デオを見ました。 (Would I need 、 after それから? Does it sound right? )

Japanese has very few rules about using 、. It is fine there. It may not be necessary, but it is OK. The rules in Japanese are far less...helpful to learners...than the rules in English.

I dislike cold mornings.
私は寒い明日がきらいです。 (does this sound right)

You said you dislike cold tomorrows. 明日＝tomorrow, 朝=morning.

寒い朝 = a cold morning

Let's watch the movie tonight.
今晩はこの映画を見ました。 (would 今晩 need to be the topic? It just doesn't sound quite right to me.)

You said "we watched," not "let's watch." "Let's watch" = 見ましょう or 見よう.

I think you really, really need to slow down and re-read everything. You have a particularly obvious problem with particles, even in the simplest of sentences. You also appear not to have read anything about the volitional form. I know that comes very early in Yookoso! textbooks. It probably comes early in Genki, too.

Go back to practically the beginning and work more slowly. My best guess is that you're moving on to new things before understanding the first things, considering you made pretty basic mistakes in every example.