Character elevation issues (Genshin Impact)

After completing the task of raising rank 1 at rank 25, I found that I forgot to raise the level of heroes (I know that it was stupid) As a result, I got stuck with the Persians of level 40 in the 3rd level of the world, Straight a vicious circle: to raise at least one hero you need to knock out materials, but with bosses of 50 levels, it becomes unrealistically difficult. Has anyone encountered a similar situation? Is it possible to cope here alone, or just try to attract friends?