As I’ve been studying Japanese I’ve found you need to train your ear in hearing Japanese. Listen to things you don’t understand and at a faster speed then is comfortable. Over time you will begin to parse out individual words even if you don’t know the meaning. You definitely need the script in Japanese to help with this. After listening for a while, listen while reading the script in Japanese, look up words you don’t know and find an English translation or use a translator that’s built into apps such as Midori, Imiwa and Wakaru. Slowly over time you will see improvement. This can be frustrating and that’s why slowly is in bold.
I came across a video and article on other sites that iterate the same thing.
That’s why I believe listening to the Bible in Japanese is good practice because the Japanese “script” is readily available in many formats (hard copy, online and in apps). I remember when I first started trying to listen to the Gospel of John in Japanese. I could hardly understand anything, but over time it slowly got better after listening to the audio, following along in Japanese and then seeing the English translation. You can even get Bibles with furigana over the Japanese.
Below is a link from The Word Project with the text of John Chapter 1 in Japanese (Kougouyaku) along with playable audio, and below that is a screenshot of the page. You can find the English translation online or in your own Bible. Try it out and keep at. Over time you will see progress.
I would supplement your listening/script reading with other sources such as Japanese news. You can easily find Japanese news along with the scripts online and use the translation feature in the Midori, Imiwa and Wakaru apps as well as online tools to get the English meaning.
Below is a website with list of features of the Midori app. I find this app very useful in studying Japanese.