Parkinson's disease can cause slow or unsteady walking and balance problems that raise the risk of falls. This study will test whether adding a gentle, non-invasive brain stimulation called transcranial direct current stimulation (tDCS) during a supervised Nordic Walking program improves mobility in people with Parkinson's disease. Participants will be randomly assigned to receive either active tDCS or an inactive (sham) procedure that feels the same but does not deliver current, while both groups complete the same supervised walking program. Sessions occur three times per week for four weeks. We will measure walking speed with a 10-Meter Walk Test as the main outcome, and also evaluate balance, motor symptoms, quality of life, and any side effects. We expect that tDCS given during the walking sessions will help people walk faster and feel steadier compared with the walking program alone.