承担许诺是一种很怪异的说法。一般说兑现许诺。

查找 look up 寻找 look for

中文 refers to both speaking and writing 
while 汉语 mostly refers to speaking. 

说 mostly with the content, 讲 expresses an abstract concept of saying something, for example 讲话，讲故事，讲课

the 相比…而言 is a fixed constructure. adding 的话 to a sentence makes it a consumption, something like the if clause in English. BTW, I think it's a correct sentence.

幸运 Xìngyùn fortunately, luckily, fortune, lucky
解释 Jǐeshì explain, expound, interpret
放弃 Fàngqì to give up, abandon, renounce
建议 Jiànyì propose, suggest,  recommend
合适 Héshì suitable, appropriate, right
参观 Cānguān visit, have a look around
连.....都 Lián....dōu even
既然.... 就 Jìrán....jìu since.....then

幸运的是, 我们的假期里没有下雨。
Xìngyùn de shì, women de jiàqī de shíhòu, méiyǒu xìa yǔ
Luckily, It didn't rain when we were on holiday.

如果你必须解释一个笑话，它就不再好笑。
Rúguǒ nǐ bìxū jǐeshì yí gè xiàohuà, xiàohuà jìu bùzài hǎoxiào.
If you have to explain a joke, then it is no longer funny.

因为他认为他的体重太重了，所以他决定放弃吃巧克力。

although it is grammartically correct, we usually don't say 放弃做什么。you can say 不再吃巧克力。

Yīnwei tā rènwéi tā de tǐzhòng tài duō le, suǒyǐ tā juédìng huì fàngqì chī qiǎokèlì.
He decided to give up eating chocolate because he weighted too much.

这是建议还是命令？
Zhè gè shì yī diǎn jiànyì huòzhě yī dāo mìnglìng ma?
Is that a suggestion or an order?

我认为这点建议并不适用现在的情况。
Wǒ rènwéi zhè diǎn jiànyì duì xiànzài de qíngkuàng bù héshì.
I don't think that suggestion is suitable for the current situation.

下个礼拜这些孩子们会去参观一家动物园。
Xià ge lǐbài zhè xīe háizimen huì cānguān yī jiā dòngwùyuán.
Next week, the children will visit the zoo.

这里的土地贫瘠得连土豆都不长。
Zhè tǔdì shì zěnme pínjí de lián tǔdòu dōu zài zhè'r bù huì zhòngzhí.
This land is so barren that even potatoes won't grow here.

既然他承诺了会带孩子们去公园，他现在就得去。
Jìrán tā chéngnuò le huì dài háizimen wèi gōngyuán, jìu xiànzài děi zuò le.
Since he promised he would take the kids to the park, he has to do it now.

**高中跟佩斯大学的孔子学院和孔子学院总部(国家汉办)有合作，这为**高中的汉语语言项目带来了很多机会。没有国家汉办的帮助，这次旅行不能成行。

I guess the plural form should be correct