Mommy, hello! My daughter got sick for the first time. She had a fever…

Mommy, hello! My daughter got sick for the first time. She had a fever for three days, runny nose and cough. One pediatrician said it was because of teeth, but it turned out not to be. We even took tests. She feels better now, but phlegm is still there. How can I get rid of it? She coughed and sputtered in the morning and felt better. What can I do? Drainage massage doesn't work. He's an active child, so he needs to lie down and run off somewhere immediately.