Placing walls, fences, and painting walls has HORRIBLE lag.

So admittedly, my lot is $8.5 million and is a little...over built (See BEAUTIFUL attached picture). I REALLY want to finish this project but the lag when placing walls, fencing, and painting walls has gotten so bad it is totally game-killing. Is there anything I can do to fix this problem?

SPECS:

OS Name    Microsoft Windows 10 Home
Version    10.0.17134 Build 17134
Other OS Description     Not Available
OS Manufacturer    Microsoft Corporation
System Name    DESKTOP-F3G5M63
System Manufacturer    Dell Inc.
System Model    Inspiron 15 7000 Gaming
System Type    x64-based PC
System SKU    0798
Processor    Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, 2501 Mhz, 4 Core(s), 4 Logical Processor(s)
BIOS Version/Date    Dell Inc. 01.00.06, 4/26/2017

Installed Physical Memory (RAM)    8.00 GB
Total Physical Memory    7.87 GB
Available Physical Memory    1.20 GB
Total Virtual Memory    17.4 GB
Available Virtual Memory    2.39 GB
Page File Space    9.50 GB