Translation:I think Chinese grammar is not very difficult.
I have the opposite experience. I learned Spanish in six months without a teacher and it's full of tenses, plurals, agreement, etc. But the order of longer sentences in Chinese with relative clauses, verbs with complements with de, and multi-character verbs where you repeat the first character all give me more trouble than the tones or reading and writing.
If your native language is English or some similar language (like Romance/Germanic), then your experience is not too surprising. Spanish mainly boils down to learning correct conjugation for a few tenses, conditional and subjunctive. Other than that, it is very similar to English, and one can apply most basic principles one is used to from their native language -- making Spanish one of the easiest (possibly even the easiest) language to learn for a speaker of a Romance/Germanic language. As for Chinese, I find it likely we're just not used to the grammar patterns. From a more objective perspective (someone speaking a language with little similarity to either Chinese or Spanish), Chinese grammar would probably be considered easier due to its lack of flexion.
I feel like it's easier than English grammar even though I am a native English speaker. I mean, what's up with adjectives that start with "in"? It could either mean that the adjective could either be "very" or "not at all"! Invaluable means very valuable. Inconceivable means not conceivable at all. Thank you for coming to my TED talk/rant