QGIS - Merge a polygon line that is splitted

Verry much a beginner at this but i have some data that contains trails that are split into smaller sections, id like to be able to merge those small sections into longer trailes based on the close proximity between the parts, how to do this? In total i have about 4000 of those small lines that i need to merge together to make about a total of 100 longer lines/trails.

Above is an example where i have highlighted an example of this.

I have read something about using buffer at 0 width but that does not seme to work for me, and when i use a higher buffer width im getting buffered with doubble the amount of points.

I have also worked with dissolve but that gives me all of thracks joind together into one big entity, i still want them to be split apart, so in the image id like to end up with 4 different tracks.