简单点解释吧（毕竟我还只是高中生无法讲出很系统的语法知识= =）：

older指生理意义上的“年长的”
eg:He's older than me

elder指有血缘关系的、有亲戚关系意义上的“年长的”
eg:He's my elder brother

farther指现实的可测量的“更远的”
further侧重于抽象意义上的“深入的”，如我将和你进行一次深入的对话
I am about to have a further conversation with you.

希望可以帮到楼主，如果有语法错误或者解释有误的话，
希望多多包涵！给我指出来~

further to...中文是什麽意思？

further: 更远，进一步 这句话的意思是：上午我们通了电话，我这是接着我们在电话上说的写。 一般是电话上说了什么事（公务、商务之类），约定了双方或其中一方往下需要做什么（如进一步向对方提供材料，作进一步的计划，把一些内容在纸上落实，等等），这方要用写信给对方的形式把这事继续向前推进，会写你写的这句话。

the further the better是什么意思？

越远越好，

further 一般指学业上的深造，所以应该是，学得越多越好吧。

你没有些请具体语境，不好判断O(∩_∩)O~

far,father,futher的区别

修改一下
应该是further

Far
[美] [fɑr] [英] [fɑː]
形容词 ( farther, further; farthest, furthest )
远的;遥远的;久远的
Manchester is farther from London than Oxford is. 曼彻斯特比牛津离伦敦远。
How far is it from your office to the bank? 你的办公室离银行多远?
较远的;那一边的;对面的
He lived on the far side of the hill. 他住在山的那一边。
(政治立场)极端的
He belongs to the far left. 他属于极左派。
副词 ( farther, further; farthest, furthest )
远;遥远地;久远地
It happened far back in the past. 这事发生在久远的过去。
He didn't go far. 他没有走远。
到很深的程度;到很远的距离
He often works far into the night. 他常常工作到深夜。
They went far into the forest to pursue the wounded bear. 他们深入森林,追捕那只受伤的熊。
到很大程度;很;极
It turned out far better than I had expected. 结果比我预料的好得多。
The room was small and contained far too much furniture. 房间太小,而家具太多。
名词
远方;远处
You haven't far to go now. 现在你无需走很远了。

father [美] [ˈfɑðɚ] [英] [ˈfɑːðə]
名词 ( pl. fathers )
父亲,父
You have been like a father to me. 你一直像父亲一样待我。
创始人;设计者;发明者
George Washington is called the father of his country. 乔治·华盛顿被称为国父。
A.G. Bell was the father of the telephone. 贝尔是电话的发明者。
祖先;前辈
They still follow the tradition of their fathers. 他们仍然继承着他们祖先的传统。
(大写)神父
(大写)上帝;圣父
动词（及物） ( fathered; fathered; fathering )
做...的父亲
He fathered a daughter at the age of fifty. 他五十岁时生下一个女儿。
创始;创立
Einstein fathered relativity. 爱因斯坦创立了相对论。

[美] [ˈfɝðɚ] [英] [ˈfəːðə]
形容词
更远的;较远的
另外的;进一步的;深一层的
Do you need further help? 你还需要帮忙吗?
副词
更远地
进一步地;深一层地
We will help you further. 我们会进一步帮助你的。
而且;另外;再者
The house is not big enough for us; and further, it is too far from the town. 这房子对我们来说太小了;再者,它离城也太远。
动词（及物） ( furthered; furthered; furthering )
促进;助长;推动
He did his best to further the interests of his state. 他尽力(或倾全力)去增进他的州的利益。