I learned Japanese for many years in my teens. And I certainly remember that the most common way to make a sentence into a question, or to recognize a question, was that it ends in "ka". Mandarin has a similar word in
It's often translated as a question mark. If you look carefully, you can see that the character has two characters (or radicals) within it. On the left is 口 (Kǒu) which means "mouth". That provides part of the meaning. On the right is 马 (Mǎ) which means "horse". It's used to provide the sound, not the meaning.
Let's see an example:
你有朋友。(Nǐ yǒu péngyǒu.)
That literally is "You have friend", but more likely "You have friends".
If we add the question mark:
你有朋友吗？(Nǐ yǒu péngyǒu ma?)
And it becomes "Do you have friends?"
Note that even in English, we could use the sentence "You have friends", as a question, just by changing the tone of how we say it.
I'll write more soon on the best methods for learning Mandarin. If you want to get a taste for it in the meantime though, my current favorite site is iTalki, and my favorite teacher by far is Amy He. If you decide to try it, click here and it's cheaper for both you and me.