I see the Japanese symbols, but never asked myself how hard is to write using these symbols. It seems very inviable. How do you guys do when writing at Japanese? Is it really harder than, for example, English or Portuguese. I mean, the amount of writing required to express the same sentence.
As I've explained when teaching, each language's quirks add value to it or else they wouldn't be retained. If you embrace the differences by learning Kana quickly and then not being afraid of Kanji thereafter, it will come fairly easily with practice. If you view kanji as a monolithic set of thousands of symbols with nothing in common with each other, you're going to have a hard time.
The trick with Kanji in particular is to remember that it forms a visual system of roots, prefixes, and suffixes that, among other things, enable you to guess the meanings of words you've never seen before or "coin" new words on the fly when needed. Further, if you become acquainted with the breakdown of kanji as you learn them you'll discover patterns (visual, semantic, and phonetic) that create a useful web of knowledge for holding everything together.
In short, it's as hard as you choose to make it.
Like others have said this is highly opinion based. I like to think of the structures as art works and have their own flow. If you look up videos of japanese students and natives writing kanji and certain hiragana words, you can notice those little nuances that can make your writing legible to natives.
Think about why english (romanized language) was easy. You learned young - were awful at the start - then a few years of schooling later you developed your own style. It just takes practice!
What you can do to practice is make haikus on paper in all japanese. It builds an understanding of the language and lets you write it out and practice.