I'm learning Japanese but do I have to learn kanji, because I don't want to learn 50,000 letters.
You don't need kanji to speak Japanese, but I would suggest that not learning kanji would make learning the vocabulary harder.
You don't strictly need to know kanji to write understandable Japanese. However, if you do write entirely in kana it will make your writing incredibly difficult for other people to read.
50,000 is a big exaggeration. The standard list is a little over 2000 kanji.
You didn't ask, but if you want to read Japanese you will make almost no progress without learning kanji.
In short, learn kanji. It's hard but it can be fun and very rewarding.
See how many kanji and by the way as a additional information, how much vocabulary you need to learn for the different levels of the JLPT Test:
- JLPT Test, N1, 2000 Kanji, 10.000 vocabulary
- JLPT Test, N2, 1000 Kanji, 6.000 vocabulary
- JLPT Test, N3, 650 Kanji, 3.000 vocabulary
- JLPT Test, N4, 320 Kanji, 1.500 vocabulary
- JLPT Test, N5, 120 Kanji, 800 vocabulary
I hope this helps to estimate the effort required to learn Japanese.
The short answer is 'Yes'. But it's not as simple as that, obviously. Proficiency is a spectrum. And knowledge of kanji is integral for an all-round development of Japanese ability in other areas. It's a misnomer that you don't need kanji. The better your kanji knowledge is, the richer your vocabulary will be, the deeper your understanding of grammar will be, and the sooner you will be able integrate new information into your interlanguage skills.
It's not about knowing kanji or not knowing kanji. Just treat it as another part of expanding your Japanese language skills. Practise your receptive skills (listening and reading) and practise your productive skills (speaking and writing). Kanji will help you develop as a learner. Don't see it as an obstacle. See it as an opportunity.
And by the way, knowledge of even around 1000 kanji will allow you to read and understand a lot of authentic Japanese materials like blogs, novels, newspaper articles, manga, etc.
If you only want to speak Japanese, writing will be less important. I think that you will eventually reach a ceiling on how well you can speak it, though-- to reach a reasonably natural degree of speaking ability eventually you'll have to interact with written material which assumes you can read at least some kanji.
If you want to write Japanese then kanji is pretty important. You don't need to learn anywhere near 50,000, but writing only in hiragana and katakana will come across as juvenile and not truly literate. You will also have trouble reading Japanese, as not all material has a phonetic version available.
I do not think that you need to learn all the kanji to write Japanese. You could just learn the most simple ones, like the kanji for "Japanese", or "sun", or "moon".
These days, not many people are able to remember and recognize the 50,000 kanji. Most people are only able to read 2,000 kanji. Still, you do not need to learn all 2,000 just to be able to speak and write Japanese. Like I said, just learn the most basic one.
Kanji will no doubt take some time to learn, but it will certainly be worth it.