If you're genuinely serious about it , I'll give you my best advice I can.
Start off learning the hiragana and katakana. Try your best to drop romaji. It's hard to progress if you can't learn to read first. Make flash cards, color code them, listen to alphabet songs, whatever helps you remember it best. Kanji can wait once you're comfortable recognizing each letter.
Once you can read , buy a Japanese dictionary. Have people correct your grammar. Search YouTube videos, there's tons. And google had tons of grammar guides. Read children's books. Any words you don't know, use your dictionary. Try to recognize common words. Pay attention to expression in people's voices to grasp how the language flows. Google image words to get better visuals. Learn the history of kanji meanings. It helps visualize better and remember their meaning.
Push yourself to think in the language. Maybe change your phone language to Japanese when you feel comfortable. Surround yourself as much as you can to use the language. Study study study. In time you'll improve ^^