Not all of my transaction is visible on electrums history tab. I imported all of the private keys into electrum from armory. But I did notice that there are some transactions that I can't see.
I don't have a clue why and I can't find any setting that seems to help me.
It's likely you missed out some private keys of certain change addresses you used. Try cross-checking and ensure you imported all the addresses you used to electrum wallet.
In electrum I can only see the first one and the size is the outputs not the amount in btc that I did send, is it possible to change that as well?
What do you mean by the bolded part? Can you please send a screenshot if you don't mind?