Video playback freezes and lags

I started having this issue a few weeks ago, and I've tried a lot to fix it. The issue is the playback. Whenever I try to playback my timeline, it plays normally for about a second, but then starts to lag badly and sometimes freeze completely, while the audio keeps playing at the correct speed. I've tried setting the Playback Resolution to the lowest it can go (1/4), I've tried creating Proxies, and I've tried setting the RAM used for other applications to the lowest it can go. It's almost impossible to work the software with the lag being produced and I would really appreciate some help. I am not very skilled in the technical area of the software, so please try to explain things as simply as you can. If you need me to provide any additional information, I will. I am using Adobe Premiere Pro CC 2018 version 12.1.0 (Build 186). I am running a Windows 10 64 bit machine with an AMD Ryzen 5 1400 Quad Core Processor, 3200 Mhz, 4 Cores, 8 Logical Processors, 8 GB of RAM with 6.5 GB available for Premiere Pro, and a GeForce GTX 970 graphics card. Thank you!