While doing exercises on my book I found some sentences with a use of 要 which I've never seen before and I can't figure out the meaning. The sentences are the following:
他很忙,但是他应该要来参加我的生日晚会
要实现梦想不是一件容易的事 and 要把汉语学好不是一件容易的事
All three examples can be interpreted as a future auxiliary.
他很忙,但是他「應該要」來參加我的生日晚會
He is very busy, but he「should be」coming to my evening birthday party.
This「要」is used in the sense of will, going to, like 我明天要上學 (I will be going to school tomorrow). Similarly,
要實現夢想不是一件容易的事
To realise (one's) dreams is not an easy matter
要把漢語學好不是一件容易的事
To learn Chinese well is not an easy matter
但是他應該要來參加我的生日晚會
means but he should be coming to my evening birthday party. To say he should have attended, you wouldn't use 要; the Chinese would be just 他(昨天)應該來參加我的生日晚會
(replace 昨天 with some other past event indicator).
他很忙,但是他应该要来参加我的生日晚会
The usage of 要 denotes the future tense in this sentence. But I'd rather use 会 instead.
他很忙,但是他应该会来参加我的生日晚会
In my opinion, 应该会 and 一定要 are normal collocations. So, it's also correct to say 他很忙,但是他一定要来参加我的生日晚会, but the tone is stronger than 应该会. 一定要 denotes a sense of "must" and 应该会 is "should" or "would".
要实现梦想不是一件容易的事 and 要把汉语学好不是一件容易的事
要, in these two sentences, is different from the first one. It's short for 想要, meaning 'want', 'wish', 'intend', and etc. These two sentences can be paraphrased as:
想要实现梦想不是一件容易的事 and 想要把汉语学好不是一件容易的事
or
想实现梦想不是一件容易的事 and 想把汉语学好不是一件容易的事
The literal translation into English might be stilted. That might be because the convention between English and Chinese is different . It could be something like:
If you want to achieve your dream, that would not be an easy thing to do.
If you want to learn Chinese language well, that would not be an easy thing to do.
More idiomatic sentences to interpret them in English could be:
It would not be an easy thing for one to achieve his dream.
It would not be an easy thing for one to learn Chinese language well.