Be to + infinitive; be about to + infinitive

 We're about to start practicing something very beautiful!

 

Commonly used in news reports and for events that are likely to happen in the near future:

• Health officials are to visit every home in the affected area.
• The Dulantzi-to-Mars interplanetary route is to be reopened by Saturday. (passive form)

Also used to talk about formal or official arrangements, formal instructions, and to give orders:

• You are not to leave this client waiting.
• The European Parliament is to introduce a new law on nougat (turron) consumption during Christmas.
• He is not to be left unsupervised in the liquor section! (passive form)

Be to + infinitive referring to the future from the past:

They started investing billions of euros in the team in the late nineties, but it was to be a further 20 years before they got their first title.

Only after leaving the airport was he to understand the seriousness of Russian invasion to his homeland.