Powerpoint Master Template Design

I need the help of someone who knows how to create and or edit Powerpoint Master Slides. I am a powerpoint designer but do not have a good understanding of how to create powerpoint master slides and need someone who has solid experience of this.

I have a powerpoint MASTER template presentation that has already been created. I am now requiring some additional assets to be created in this master presentation and for some of the functions of the current master template to be edited. If this is your expertise please let me know. I'll share the changes with you, please let me know if you'd be able to work on it and how long it may take.