1-I CANNOT pray ALL the hours, it does not work for me, BUT I can do most of them. Is that ok? Can I still pay the hours if I only do some of them?
2What is proper posture while praying the Divine Office?
3-How do I learn to chant?
OraLabora, one of my favorite posters, usually offers his advice with regard to Liturgy of the Hours threads, and I hope he’ll do so with this one, too.
But for the present: we lay people can pray as many or as few of the hours as we please. Praying all of the hours is reserved for those who “have received a special mandate to carry out the Liturgy of the Hours: bishops and priests as they pray in virtue of their office for their own people and for the whole people of God; other sacred ministers, and also religious [General Instruction of the Liturgy of the Hours, no. 17].”
As for postures, that depends on if you are praying privately or in common. The postures for the latter are described in the above document, starting at paragraph 263. If you’re praying privately, then I don’t believe there is anything in particular that is prescribed.
Here is a link to the document:
ewtn.com/library/curia/cdwgilh.htm#Ch%20I
As for chant, I’m not sure how this is accomplished without purchasing additional books that have some form of musical notation. At our parish, when we chant Evening Prayer together, we usually use a generic melody for each line, as lead by one of our priests. But I know so little about liturgical music I couldn’t even begin to say more about all of this.