The phrase "heaven" and earth" represents everything that exists. Alternate translation: "Master over everyone and everything in heaven and earth" (See: [[rc://en/ta/man/translate/figs-merism]])
This refers to Jesus' previous teaching about the authority of the disciples. It may be best to simply say "these things" and let the reader determine the meaning.
The words "wise" and "understanding" are nominal adjectives that refer to people with these qualities. Because God had concealed truth from them, these people were not actually wise and understanding, even though they thought they were. Alternate translation: "from people who think they are wise and have understanding" (See: [[rc://en/ta/man/translate/figs-irony]] and [[rc://en/ta/man/translate/figs-nominaladj]])
This refers to those who may not have much education but who are willing to accept Jesus' teachings in the same way that little children willingly listen to those they trust. Alternate translation: "people who may have little education, but who listen to God as little children do" (See: [[rc://en/ta/man/translate/figs-ellipsis]] and [[rc://en/ta/man/translate/figs-simile]])