日本語を勉強します！！

二年間日本語を勉強していますが、まだ日本語がわかりません。日本語はとても難しい。単語がわからない。文法もわからない。
でも日本語を勉強します！

The best way I found was to find a hiragana chart and practice. I know it sounds old school, but repetition works. Repetition does work. Once you are more familiar with the characters you can test yourself by spelling out simple words or phrases you know in hiragana and see if you are right. This also improves your vocabulary. Once I know my hiragana, I will test it.... I know "Nihon" or "Nippon" is how you pronounce Japan in Japanese, so I will spell it in hiragana, testing my characters and memory. に　ほ　ん When you are more familiar with the language and the characters, you could move onto simple sentences, always using your hiragana.

Yes, it means that up until this point everything is going well. As for the connotation, it really depends on the context in which you use it. You could use it cautiously optimistically or neutrally. Stating that things are going well is not exactly pessimistic and you would usually not use "So far so good." in such a context. Cautious optimism: Trying something for the first time, such as sewing. You are stitching and the instructor/your grandma/your mom/someone asks: "How is it going?" You: "So far, so good." (In a tentative voice) could be cautious optimism. If you were more absorbed in your work and were replying more curtly, it would come off as a neutral statement.

It does make sense, so long as you have previously described the "that" your sentence is referring to. If you wish it to be a positive statement, something you are certain about, you should say that "That is why this [right now] is the right time...." "I believe this could be..." states that there could be some doubts or that you hold doubts in your own statement. Saying something is, rather than could be, conveys confidence and affirmation in your statement. Hope that helps!

The first is stating a fact: If you come this way, I will lead you to the office. It is fact. The second is a little strange in spoken language, but it is giving "you" the option to come or not. The third is probably most common spoken. It is a polite way of suggesting that "you" go in a direction to be led to the office.

The way I interpret the phrase would be to mean that the clean-energy startups cost multimillion dollars. Without a proper context in which to view the phrase, it is all speculation, but I take it to mean that clean-energy startups are not cheap, unfortunately.

If both parties are aware you are talking about a jacket, you would simply respond with "I take a medium." or "I am a medium.". For the most part, though sizes are printed with letter representations, we would not say "size M" in any context.