multi variate time forecasting

I want to forecast in a time serie the 'output'. I have from the past the correlated time series 'output', 'capacity' and 'load'. I also know from the nearby future the time series from the 'capacity' and 'load'. See picture. I'm looking for a solution to this problem in python. All variable have the same unit in man-hours per hour (mh/h). For your interest; the output is the work that is finished in a skill group based on the baseline. Normally when the load is much higher than the capacity the output will drop because of overload effect on people. Basically the output is the actual capacity the skill group can perform and not the assumed capacity in this graph. It is vital to find out what the output in the future can become.