I just used the same fee as the $622 transaction but I can see now that the $ 20 transaction is over double the size in bytes silly me thought the bigger the money value the bigger the size, I am new to this and it's so interesting and my word after reading this forum all night ye guys know a lot
It's a common misconception. A standard fee or a fixed fee is a very bad idea. The required fee is usually dependent on two things:
1) Recommended fee rate at time of transacting (see the link I included in my previous post).
2) Transaction size.
Can I ask do you have to do one transaction at a time ? and does it mean all the remaining balance is unusable while there is a transaction waiting for a confirmation ?
The answer is yes and no. It depends on the scenario. For example:
If you only have 1 address (1 output), therefore only 1 input to include in the creation of a transaction, you can send one. Your change balance is unconfirmed. Whilst you can create a TX with this balance as well, it's somewhat pointless as it won't confirm until the previous one does.
If you have multiple (outputs), therefore multiple inputs to select with coin control (e.g. in Core), then you can create several. For example:
Input (A) -> TX (A) -> Send to Bob.
Input (B) -> TX (B) -> Send to Satoshi.
...
I'm not fully familiar with the options that Multibit provides. However, Bitcoin Core provides a very good feature called 'coin control' (specifying inputs and custom change address).