Using the App "Human Japanese" on both the App Store and Google Play store is a good way to start. It is basically a digitised text book with quizzes at the end of each chapter. It also has recordings of pronunciations. It is around $12, but it is quite cheap compared to most textbooks (especially the one I had to get for uni). Flashcards is another very good way to remember vocab, kana, kanji, and even phrases/sentence structure. Flashcards are your friends! Use them! I personally use an app on my phone rather than physical flashcards. It is more convenient, saves paper, and is with you everywhere.

Group 1 verbs that end with 「る」 will have the form of 「って」while group 2 verbs ending with 「る」will have the form 「て」 As a general rule, verbs that end with "~iru" or "~eru" are group 2 verbs and will end with 「て」 However, be careful, there are exceptions, some verbs ending with "~iru" or "~eru" can be group 1 verbs (such as 帰る (kaeru))