My understanding of the us civil war is that the northern economy didn't depend on slavery anymore, and thus it was possible to abolish slavery, whilst the south still depended on slavery and thus couldn't afford to get rid of it.
What was it that made is possible for the north to do away with slavery but not the south,
was i the nature of the products produced in the north, or advancements in machinery(i know that the south didn't have the economy to produce advanced weapons and ammo, maybe this is related)
So how did the southern economy react to the sudden loss of labor?
Was there a sudden push for implementing machines to lighten the work of farmers?
If black people were suddenly freed in large numbers, where did they go?, did they keep working for their former owner for almost no money or look for a different means of living?(i understand that there is a large amount of variation here due to individual people making individual choices, but i mean in general)
And if this isn't to speculative, would it have been possible to avoid the war altogether by first implementing changes in the way things were produced in the south and then abolishing slavery?
This is a huge topic with lots of elements, but very early migration patterns and economic trends shaped the differences between Northern and Southern slavery. The differences in who came to which parts of what became America, the cultures they brought with them, and the parts of English society from which they came was decisive. It's older, but David Hackett Fischer's Albion's Seed: Four British Folkways in America (Oxford, 1989) is excellent at exploring this.
Settlers to New England in the 1630s were puritans--religiously-motivated individuals. They organised themselves into villages in which family-run farms were the basic economic unit, an extension of the practices of the South-East of England from which they came. Slavery in rural New England, especially in early rural New England, aligned with this, where enslaved people were within households.
Please note that I'm not in any way implying that this was good for enslaved people, that they were 'part of the family' in a modern sense, or that it was in any way a kindness or benevolence to be enslaved by puritans. My only point is that the basic economic unit was a family in which everybody had roles in farm production, and enslaved labor supplemented this. Individuals who weren't enslavers could and would still hire the labor of enslaved people and pay the owners, thus participating in slavery without owning anybody.
Southern colonies were largely aristocratic and hierarchical in governance. They created a system of plantations, based on large individual landholders. This in turn replicated the elitist English systems in which many of Virginia's early "leading" families benefitted. Plantations produced cash crops--indigo, cotton, tobacco--for export. This was similar to a system found in the West Indies, where sugar dominated. The brutal nature of sugar production meant that many landowners enslaved people rather than try to persuade individuals to endure the conditions for wages.
As families grew in New England and small-scale industry developed alongside it (ie, broom-making in Western Massachusetts, based on local agricultural products), slavery became less relevant. However, the profits of slavery, especially after the invention of the cotton gin, made the plantation system in much of the South all the more lucrative.
It's important to note that through the nineteenth century, even after many New England states had abolished or ended slavery in different forms (court cases, gradual emancipation, etc), the newly-industrial North often relied on cheap Southern cotton in its textile mills. Why was the cotton so cheap? Slavery. So much of the Northern economy was, in fact, benefitting from slavery even if slavery no longer existed in the Northern states.
For a good, accessible analysis of the pre-Civil War economic and political issues, I'm a fan of the Oxford History of the United States series. The two relevant volumes are Daniel Walker Howe's What Hath God Wrought: The Transformation of America, 1815-1848 (Oxford, 2007) and James McPherson's Battle Cry of Freedom: The Civil War Era (Oxford, 1987).
For post-war labor issues, go to Eric Foner's Reconstruction: America's Unfinished Revolution, 1863-1877 (Harper, updated edition 2014). Specialists in this are can recommend other texts and address the very fraught issues of post Civil War labor rights.