Need iOS GPUImage Expert for photo and video slideshow app

I've had a slideshow app developed that allows users to select photos and videos to create slideshows with music. Most of the app design and UI is completed already but the existing developer is struggling to have the features where the app can combine photos and video clips together to make a slideshow. We also need the ability to add transition effects between the different photo/ video selections when they playback in the slideshow videos. Please type the number 23 in your response so that I know you've read these details.

The UI of the app was made using swift and the slideshow functionality is using objective c. The photo-photo slideshow function was made with GPUImage. So I am looking for a GPUImage expert to make the photo-video, video-video slideshow components.