I highly doubt that adult 1700 on lichess will ever achieve IM title, let alone in 3 months.
Chess is one of the games in which one needs to develop a feeling for in the youth, it's very hard to accustom your brain to the game in the adulthood.
It's not only about studying some opening lines or thematic endgames, it's about solving specific kind of problems over the board which generally do not have a definite solution and one has to rely upon his intuition greatly, also most of chess player's thought are actually going subconsciously, just ask any really strong player how did he come up with a come, you'll notice that he has hard time explaining the process.
I've merely scratched the surface here, if you want to go deeper down the rabbit hole I suggest you to read Chess for zebras by Jonathan Rowson, an excellent grandmaster and psychologist.
Chess is one of the games in which one needs to develop a feeling for in the youth, it's very hard to accustom your brain to the game in the adulthood.
It's not only about studying some opening lines or thematic endgames, it's about solving specific kind of problems over the board which generally do not have a definite solution and one has to rely upon his intuition greatly, also most of chess player's thought are actually going subconsciously, just ask any really strong player how did he come up with a come, you'll notice that he has hard time explaining the process.
I've merely scratched the surface here, if you want to go deeper down the rabbit hole I suggest you to read Chess for zebras by Jonathan Rowson, an excellent grandmaster and psychologist.