So if I understand correctly it doesnt make a request with only the address that is personally being used but it downloads the entire last block(?) and it check if the transaction is found?
No. It tells the peer to set a specific bloom filter. That filter means that if any part of a transaction (hash, outputs, inputs, etc) matches that filter (i.e. do some operations with the filter and if it matches one thing should return and if not, a different one). If there is a match, it will relay that transaction to multibit, otherwise it will not. Multibit then has to check the transaction itself to see if it pertains to the wallet. Bloom filters have the effect of having false positives but no false negatives. That means that every transaction that the peer relays to Multibit may not actually pertain to the wallet, but the wallet will receive every transaction that pertains to it.
