Isn't 14 days of treatment with Nilogrin too short?

was prescribed to the son (15 years) nilogrin 10mg 1-1-0 for complications after covid – terrible weakness, impaired concentration, balance, etc. already on the second day of admission there is a significant improvement. He is to take it 14 days and the end. Isn't that too short? Can those horrible symptoms that were still come back? I'm terribly afraid of it, because it's a terrible condition, and on this drug my child normalized