Michele Bolzenaro posted this as direct message to me and I am adding it here
Can running affect my performance in a negative way, my ambicious is to be duathlete 
So for most amatures running will help their cycling performance but the important part is getting enough recovery. If you are riding a lot and don’t have time to fully recover from both running and riding then running could hurt your performance. You might want to for example do a ride in the morning and then a run in the evening, get a great night sleep and then take the next day off.
Really there are many triathletes that perform at very high levels of cycling performance so for sure it is possible. TrainingPeaks and I believe Intervals ICU as well as golden cheetah have a performance managment chart that help you manage your training load. When you are increasing your intensity or duration of one or both sports it can be very easy to over train and start going backwards. This is tricky. You also can use HRV to monitor your recovery and train based on when you are fully recovered from previous training effort.
With running specifically you might want to keep your intensity low (low HR) for example as higher intensity running can really require more recovery time.