weak results of CNN model

I have run a deep learning code, it pre-trained on the ImageNet and then trained on its dataset. The dataset is chest X-ray images and the model used for detection of covid-19 disease. The problem is that the results are so weak while in the paper the results are outstanding. I want someone who is an expert in python and TensorFlow and has the ability to write the code of pre-trained models and do the process of training exactly based on the paper. I have attached a pretrained model structure and the paper. If you think you can simulate the results exactly based on the paper try this and contact me for details.