Hello!

I need help regarding computer

It's been a while since I've posted new maps or illustrations... it's because I let myself be drawn into a project that has taken on proportions beyond my control.

At first, I wanted to design a 3D castle on Sketchup, I started by drawing elements, then I made more and more, then I started to assemble everything and with enthusiasm, I found myself modelling the palace of the largest city in the world of Nossym, on which I have been working for several years...
Here are some examples of where I stand :

Click image for larger version.  Name: Forteresse Aylesdeen 3D May.jpg  Views: 34  Size: 530.8 KB  ID: 115719

Click image for larger version.  Name: Forteresse Aylesdeen 3D MayB.jpg  Views: 32  Size: 658.6 KB  ID: 115720

Obviously, this is where the problems start: I work with layers, which allows me to work easily on each element separately (by hiding the layers I'm not working on). But when I want to see all the layers, my computer starts to show serious signs of weaknesses: it needs long computational moments and the slightest click sometimes leads to minutes of absence. The problem is that I am far from finished: I still want to design a large palace and a citadel, as well as other smaller buildings.

So here's my question:

Do you think I can change some parts of my computer to improve its computing power. It was bought in december 2015, it's a MSI GE72-2QF, Core I7, 5700 HQ, 17,3", 16GB, 2xSSD128GB+1TB, Bluray, GTX970M, Win 10 ?
Should I consider buying a new computer ?
Or, given the scope of the project, I might as well give up right away, because no personal computer has the necessary computing power...

I tried to reach the computer shop where I bought mine, I had no answers... so I turn to some specialist here, that knows a lot about those machines...

Thanks a lot in advance for your help !