"In questo modo, non perderai le tue chiavi."
Traduzione:This way, you will not lose your keys.
There's a subtle distinction in English, although both would be understood.
"In this way" implies that a particular technique or method is being taught, whereas "this way" simply means "now that a certain measure has been put in place".
For example - if you taught someone to leave their keys in a bowl every time they entered the house, "in this way" they wouldn't lose their keys; on the other hand if you gave them a keyring to hold their keys together, "this way" they wouldn't lose their keys. :)