Hi @Dhaval!
You can use the write interval of 50 to limit the size of the output. That is absolutely legit here.
Regarding your second question I do not know what you mean? @drodriguez32 explained what is to be done in every picture as far as I can see. There are no additional steps you have to do. What errors are you referring to? Maybe you can show us some plots or screenshots of what you mean. Will be happy to help you there!
Best,
Jousef