I can without much difficulty understand what’s being said.

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. I can without much difficulty understand what’s being said.
  2. I can without much difficulty to understand what’s being said.
    Is #2 correct or not?
2

No, #2 is incorrect - you need a verb to go with “can”, not an infinitive. For instance, you could say “I can without much difficulty manage to understand what’s being said.”

3

Although #1 is possible, for me the natural word order is “I can understand what’s being said without much difficulty.”