I tried some courses. Some courses are good to learn from first, but lots of courses are difficult, and there are no text(videos only), so it takes time to try.
Unreal Engine 4で極めるゲーム開発: サンプルデータと動画で学ぶUE4ゲーム制作プロジェクト
I think this is a really good introduction book.
その他メモ
Quixelの利用。MegaScanなど。