Is it true that evaporation causes cooling and the rate of evaporation of an aqueous solution decreases with increase in humidity?

The above statement is true.

This is because as a liquid evaporates, it absorbs the latent heat of vaporisation from 'another matter' it comes into contact with. This 'other substance' loses its heat and cools down. As a result, evaporation cools the environment. If the humidity level is high, the air is already saturated with water vapours, meaning there are a lot of them. As a result, adding more water vapours will be difficult. As a result, the rate of evaporation slows. Hence, evaporation causes cooling and the rate of evaporation of an aqueous solution decreases with increase in humidity.