It is advised to study tongue placement, but it's not an urgent thing for a beginner. Speaking practice is something we do after we learn to understand Japanese.
Unfortunately, I don't know any good tongue placement resources.
Such content is in great scarcity.
You can, however, try searching for each sound specifically
when you're not sure how to pronounce it.
E.g., search "how to pronounce the Japanese R sound" on Invidious.
There are some sounds in Japanese that require special attention (like
and some sounds that you get right away without much practice.
Imitating native speakers is also advised, but not for beginners. It's a practice people do after around a year of studying, or even later.
Imitating native speakers and speaking in general may lead to damaging results when you don't have a good foundation in listening. The sounds you are trying to pronounce don't exist in your native language. If you can't hear them quite well yet, you're setting yourself up for making and repeating mistakes.
The person you imitate should be the same gender and roughly the same age as you. There are sizable gender differences in Japanese. Men and women speak and act differently, use different expressions, pronouns and sentence endings. People also change how they speak as they age. A 75-year-old man doesn't sound the same as a 15-year-old girl. This is also true for many other languages.
The way we recommend imitating native speakers is by doing shadowing exercises. Shadowing is when you repeat what a native speaker says roughly at the same time as them. Not before or after. When shadowing, you should be able to hear both yourself and the native speaker at the same time.
Listen a lot. It's the best thing you can do until you reach a more advanced phase when you're ready to start practicing speaking.