is there anything I can do to improve my pronunciation in Japanese?
The earlier you start, the better. If you start learning any language as a teenager or later, you’re going to have a noticeable accent. Although getting rid of it completely might be impossible, you can definitely work to make your Japanese “prettier.” Here’s a couple of tips I have though:
Start with the smallest units, the sounds themselves. Find a hiragana audio chart (like this) and emulate the sounds, listening and them repeating them as best as you can. With Japanese, you’re lucky, as almost all the sounds (m, k, s, etc) are present in English as well, so making the sounds themselves shouldn’t be hard. Instead, focus on making the intonation and pronunciation sound authentic.
In particular, ら・り・る・れ・ろ shouldn’t have a strong English “r” sound, even though they’re usually written with “r”s. It’s difficult to explain, but I think the closest equivalent is the “l” in “supplies”; it’s a quick flick of the tongue off the roof of your mouth that’s weaker than the first sound either “ryes” or “lies.” Other people say it’s “halfway” between “r” and “l,” so maybe you can think of it that way.
If you’re a native English speaker, pay special attention to your pronunciation of カタカナ words. It’s very easy to slip into English pronunciation of the English words in particular. For example, remember that there is no “uh” sound in Japanese, so while you might say “Uh-me-ri-kuh” for “America” in US English, when you say アメリカ in Japanese, take care to make the アand カ have strong “ah” sounds, like “Ah-me-ri-kah.” Pay attention, maybe even record yourself speaking, and try to eliminate those weak “uh” sounds in all your words, as Japanese doesn’t have them!
Long vowels and small っ breaks are also easy to forget about when speaking. Try slightly exaggerating the length (or っ stop)to help yourself remember the words they’re in.
Keep in mind that Japanese has a pitch accent, and while it may not be as important as in, say, Chinese, it is still there. Rather than try to memorize the pitch pattern for every single word, if you consciously listen to and emulate the pitch of a Japanese conversation, you may find yourself subconsciously putting the pitch changes in your own speech. If you’re an advanced student, you can ask a native speaker to critique you; if you’re starting out, it’s honestly not that important.
Pay attention to the pitch of the larger phrases and sentences as well. Declarative sentences tend to slightly “fall” in pitch during the final verb, but if you’re asking a question, raise the pitch instead.