My mother tongue is Chinese and I find that English is the easiest second language to learn. English has more or less the same grammatical structure as Chinese, so I didn't have to learn structures like object -> subject -> verb as in Spanish or reflexive verbs or structures like "Me pleases programming" (Me gusta programar) that means "I like programming", or the sentence structure of topic -> object -> verb with all kinds of particles in Japanese. Yes, English has a few conjugations, but boy that is so much simpler than those in Spanish. And English pronunciation is easy for a Chinese, but boy other European languages are hard, as Chinese does not have alveolar R or double R as in Spanish, and don't even get me started on the pronunciations in French and German.