performances evaluation of image classification with different distribution for train and test set
I'm afraid you have too little data. That's why optimizer can't converge to any reasonable place. I'd suggest you try doing transfer learning first. Few links for you to check out:


https://machinelearningmastery.com/transfer-learning-for-deep-learning/
https://www.pyimagesearch.com/2019/05/20/transfer-learning-with-keras-and-deep-learning/
https://www.pyimagesearch.com/2019/06/24/change-input-shape-dimensions-for-fine-tuning-with-keras/
https://www.pyimagesearch.com/2019/06/03/fine-tuning-with-keras-and-deep-learning/


Consider also heavier augmentation. Albumentations is a nice repo, used in many kaggle competitions.