There is no interaction between CBD and Levodopa as they are metabolized via different mechanisms. Thus, it is safe to take them concurrently.
CBD is metabolized in the liver, mainly via the enzyme CYP3A4. And since CBD has been shown to markedly inhibit that enzyme, it can elevate the serum concentrations of drugs metabolized by that same enzyme.
However, the metabolism of levodopa is largely through peripheral or intracellular amino acid decarboxylases, with minimal hepatic (liver) metabolism.