I want to know how to use the 为, because there are cases where we dont translate it and it gets it harder so i'd like like to know the uses and effects this one provoke in the sentence.
I am no grammar expert, but let me attempt an answer based on my level of attainment. I am sure others could do better.
This is one of the most commonly occurring and useful word in the Chinese language, just about behind 的 & 了。
The problem is, (just like 的 & 了), it is a preposition, and when used in combination it becomes a verb, a conjunction, an interrogative, (a sentence of inquiry that asks for a reply)
So it is in an actual sentence that its usages become apparent.
As a preposition it is "for"; 他的牺牲是为了什么?, (his sacrifice is for what?)
As a conjunction it is "because of"; 他为爱国以牺牲了生命, (Because of his love for country he sacrificed his life)
As a verb -- 成为 -- "become"; 他的牺牲将会成为传说, (His sacrifice would become a legend)
As an interrogative -- 为什么, "why", 他为什么牺牲自己的生命?, (why did he sacrifice his own life?)
A good start is the Chinese Grammar Wiki page for 为, which I'll go through. Each of the relevant webpages have multiple examples, but I'll add some in-the-field examples.
By itself, 为 basically means "for" along with some related definitions. Perhaps the "cases where we don't translate it" arise when 为 is used within words such as 因为, 为什么, 成为, 行为, 为何, 以为, 认为, 作为, etc., where it doesn't mean "for" (it's just part of the word).
The simplest usage has the structure:
为 + Party + Verb / Adj.
Expressing "for" with "wei"
- 爸妈，今天我为你包饺子![src] (Dad and mum, today I made dumplings for you!).
- 我这次来上海为大家演讲[src] (This time, I come to Shanghai [to] make a speech for everyone).
- 为社会为世人尽力[src] (For society, for people, strive [your] hardest)
This structure is similar to:
为了 ⋯⋯ ，Subj. ⋯⋯
Expressing purpose with "weile"
为了您的身体健康，请少饮酒[src] (For your bodily health, please drink less alcohol.)
为了爸爸妈妈,我要努力![src] (For father and mother, I will try hard!)
It's also similar to:
Subj. + 为 + Goal + 而 + Efforts Made
Subj. + 不 + 为 + Goal + 而 + Efforts Made
Explaining purpose with "wei... er..."
- 为自己而学 (Learn for yourself [although more like "learn for your own reasons"])
- 为中国而战[src] (Fight for China)
There's also a song called 为爱而生 = "Live for love".
And also similar to:
⋯⋯ 是 + 为了 / 因为 ⋯⋯
Expressing purpose with "weile"
- 人来到世上是为了什么?[src] (Mankind is on earth for what?)
- 上班不是为了赚钱[src] (Going to work is not for making money.)
- 成功是因为态度[src] (Success is because of attitude.)
- 有时候,喜欢听歌不是因为歌唱的好听[src] (Sometimes, liking to listen to a song is not because the song sounds good)
The final one is similar, but follows a specific pattern:
以 + A + 为 + B
Using "yi... wei..."
- 以朋友为话题的文章[src] (An essay taking [a] friend for [the] topic)
- 以我家为例, ...[src] (Take my family for example, ...)
This is also used in a lot of idioms, e.g. 以黑为白 literally means something like "take black for white" implying something like "wrong is right".
There are several usages of 為, I just list part of it. Sometimes, 為 show that things are or are done for object after 為. For example, 他為我留了一塊蛋糕。 in English: He left a piece of cake for me. This example shows that thing was done for object after 為 (我). Sometimes, 為 shows that something after 為 is used to describe something before 為. 這餐花費為1000元。 in English: This meal cost for 1000 dollars. This example shows that something after 為 (1000元) is used to describe something before 為 (這餐花費). 成為傳奇。in English: Become a legend. This example show that somethings after 為(傳奇 in English: a legend) was used to describe something before 為(成 In English: the action of becoming something).