Rusty

Rusty is an adjective we use to describe the condition of this truck, but we can use it for other things too. If you used to do something easily, and now it's more difficult, you can say that you're rusty. Being rusty at something is usually an effect of not practicing for a while. You could be rusty at riding a bike, or cooking soemthing complex, or playing a sport. It's very common for your English to get rusty if you don't practice very much. Fortunately, if you learned something once, and learned it pretty well, it's not incredibly difficult to recover your skill, it's only a question of starting to practice again. This truck may never roll down the highway again, but you can regain your fluency in English with some practice and some patience!