***** NOT A TEACHER *****
"I know a little bit of English grammar." = present.
"I knew that he did it, but I did not tell the manager." = past.
"I have known Mona for 20 years." = "known" is the past participle.
"Knowing that he was too old, James did not even apply for that job." = "knowing" is the present participle.
Student or Learner