Simply set Gmail up to poll any other email addresses you have, you can then retrieve all of your incoming emails using the Gmail app and reply (using the gmail app) from the same address the original message was sent to.
Then, whenever you log in to Gmail, regardless of what device you're using, all of your emails are there.
since changing from an apple phone to an android one, my laptop pc does not recognise mail that has been read on my phone or show sent mail from my phone. I wonder if I can set this up ?
It would appear that if you are using an email app on your Android phone you have set it up as an POP3 account. This does not synchronise sent emails, folders etc with the BT servers which in turn means that when you do something on your phone it is not replicated on your PC.
If you want your email app on your phone to do that you will need to set up your app as an IMAP account. This will synchronise with your PC so that what you see and do on the phone will be the same on your PC and visa versa.
Unfortunately if you want to change your email app to an IMAP account you will need to delete the account that is already on your phone and then re-set it up as an IMAP account.
Before doing that make sure that you have backed up your email on your phone or at the least check that all your emails that you want are still on the BT servers by logging onto your email account via a browser.
Have a look at this link about how to set your phone's email app up as an IMAP account.