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What is this plant with little yellow flowers? The smell is immaculate, so strong, smelt from far away, yet soft and perfume like at the same time.

Plant grows maybe 2m tall.

How can I grow cuttings? Or will it grow seeds I can harvest more easily after the flowering season?

It's Osmanthus as already said in one of the other answers, specifically, Osmanthus fragrans, maybe the variety 'Conger' - there's a clear image of the flowers here https://m.dhgate.com/product/wholesale-tea-sweet-olive-osmanthus-fragrans/390370702.html#pd-019

Propagation can be done by collecting ripe seed, but they can take 6-18 months to germinate, so it's more usual to take semi ripe cuttings during early summer and use bottom heat to get them rooting, or almost ripe cuttings with a heel in autumn, placed in a cold frame. General information and propagation info here https://pfaf.org/user/Plant.aspx?LatinName=Osmanthus+fragrans

It looks like some type of Osmanthus to me. There are quite a few different species: O. heterophyllus, O. yunnanensis, O. fragrans (sweet olive), and many, many more! I think Home Depot's picture of their plant has the most resemblance to your photos:

Osmanthus can be gigantic trees or small shrubs, or can be trimmed to become hedges. Some bloom in the fall, and some in spring.

The reason I think of Osmanthus and not Pittosporum is the way the little flowers look, hiding amongst the leaves, and also the way you describe the fragrance, "... immaculate, so strong, smelt from far away, yet soft and perfume like at the same time."

The fact that you use the word "immaculate" sounds more like O. than Pittosporum which is so overpoweringly fragrant it can be cloying and unpleasant at close range. (my opinion, sorry)

Osmanthus does have a heavenly fragrance that for some reason can be very hard to pinpoint where it's coming from. Maybe because the flowers are so nondescript and "shy", you don't suspect (or even notice) them right away.

This is a Fragrant Tea Olive.
I got one from amazon couple months ago and it has bloomed couple times already in my house.
The Fragrant is exactly how you described it

Here is the link...Good Luck!
Fragrant Tea Olive on Amazon

Ok this one is tough; my choice is Pittosporum omeiense, native to China, fragrant, and the leaves look similar. My difficulty here is in finding references - the ITIS database does not recognize the species name even though it is pretty well scattered about over the Internet, and I don't have time to rake through all the possibilities. Hortus Third does not list it under that name, although it might be there under a synonym, reclassified into a different genus.