Welcome to Sciforums adalel.
Your mostly correct with your theory. Our eight planets are the last remnants of our early solar system, and have acted similarly to water droplets except they do not become molten until they are near planetoid size. The gravity of the dust starts to atrract other dust particles until a small gravity "well" forms, atracting more and more and dust. Eventually, objects the size of asteroids are formed, and other asteroid sized objects are atrracted to it. This is where the molten rocks come in. The amount of friction between the two asteroids is enough to heat the rock to a molten state. The asteroid grows and grows atrracting more and more objects, and eventually reaches planetoid size. This has to be the most chaotic part of our solar systems formation, cause now we get into planet sized collisions. Every planet would only be about the size of mercury or mars, but there would be hundreds of them. With the chaotic orbits of the planets, some of them may not even be able to complete one orbit around the sun before they encounter another planet. The planets are still growing at this point, and the largest are the only ones not being demolished. Astronomers believe that our own Earth crashed into another planet about the size of Mars and this collision made the Earth not only the size it is today, but possibly also our moon. The number of planets orbiting the sun gets smaller and smaller over time. Orbits become less and less chaotic, settling into our harmonic orbits we have today. The planets begin to cool, and collisions become less and less severe with the occasional major asteroid collision. Eventually, we have our eight planets, asteroid belt, Kuiper belt and Oort Cloud.
Hopefully this helps with your question, and feel free to ask anymore that you may have.