The TIF issue is easy to fix - just choose a different format when you export - PNG probably the best.

Import to Tensorflow\Keras generally requires some Python code to convert the images & labels into the internal data structure. It depends on what you are trying to do in Keras as to which export format would be best to use. What type of task are you doing: image classification, object detection, pixel classification? What model are you going to use in Keras: SingleShotDetector, FasterRCNN, MaskRCNN, Unet, etc.?

There will generally be some code out there that you can take and adapt to your data.