How to split test and train size

I am trying to feed a CNN model(Human body pose estimation)with a dataset contains 1000 numbers, first, how can I make sure that the number of my datasets is already enough? second, how should i split my data to train and test size? (when I put train size = 0.6 and test_size = 0.4 the network doesnt work well and show me NAN for weights and bias and loss value!)