You can use “But” to introduce a phase or clause contrasting with what has already been mentioned. Normally you can translate “But” into “Shikashi”/「しかし」in Japanese, but we have other ways to say “But”in Japanese. I will introduce 4 ways to say it.
We use it at the beginning of a sentence. We often use it not as spoken language but as written language. You can also write “Shikashinagara”/「しかしながら」. This is a really written expression, so I have never heard this in a daily conversation. I don’t recommend that you say “Shikashi”/「しかし」or “Shikashinagara”/「しかしながら」to Japanese people if you travel to Japan. We use them as written language as the following example.
I would like to go to Japan. But now I can’t go there because of CoronaVirus.
We use it at the beginning of a sentence. We often use it not as written language but as spoken language. If you use it as written language, you would give people a casual impression. In daily life I often use it and hear it. You wouldn’t give people an impolite impression even if you say it to someone whom you don’t know. I will introduce an example about how to say it.
Sushi is very delicious. But it’s a little bit expensive.
We can also just say “Kedo”/「けど」. We can use them both at the beginning and end of a sentence. We often use them not as written language but spoken language as “Demo”/「でも」. These expressions are a little bit more casual than “Demo”/「でも」. But even if you say it to someone whom you don’t know, you wouldn’t give people an impolite impression.
I would like to go to Tokyo station, but I don’t know how to go there.
I would like to eat Ramen, but I don’t have money.
We use it at the end of a sentence. We often use it not as spoken language but as written language. You can say “Ga”/「が」to Japanese people if you travel to Japan, but I think it’s unnatural. We use it as written language as the following example.
Japanese people are shy, but they are kind.
You can say “Shikashi”/「しかし」or “Ga”/「が」, but these are unnatural as spoken language. It’s better you say “Demo”/「でも」or “Dakedo”/「だけど」when you travel to Japan and talk to Japanese people.