Learn Spanish (Latin America): Este carro es muy rápido, pero yo manejo lentamente. - This car is very fast, but I drive slowly.

To make an adverb with -mente, you always start with the feminine form of the adjective. The masculine adjective for 'slow' is lento, so we change it to the feminine lenta and then add -mente to get lentamente (slowly).

Why isn't rápido written as rápidamente here?

Because rápido is describing the car itself, making it an adjective. You only add -mente to create an adverb, which is a word that describes an action. In the second half of the sentence, lentamente describes the action of driving (manejo).

I always mix up este and esto. Why do we use Este for 'This car'?

Use este when you are pointing out a specific masculine noun right next to it in the sentence, like carro. Esto is a neutral word used for abstract ideas, general situations, or objects you don't know the name of yet (like asking 'What is this?'). Since we know we are talking about a specific masculine car, we use este.

Is it possible to just say yo manejo lento instead?