If you are running low on disk space you can try clearing the Fusion local cache. Simulation will cache the results of local or cloud solve on your hard drive and eventually delete these files, but you can purge them manually. Since they are back up on the cloud you won't lose anything - it will be re-downloaded if you need it.
Go to Fusion Help = Support and Diagnostics - Clear cache data. This will require all documents to be closed as Fusion will restart. During the restart the cache will be cleared.
If you are running local solves and you want them to be faster, even though you have freed up some disk space, you just need to buy a newer, faster Macbook, there are not that many options. Just make sure you get 32 GB RAM and a lot of disk storage and the one with the fastest processor/most cores. If you want to get a Windows laptop, get something with a 10th gen core i9, up to 5.3 Ghz, 8 Core, 32 GB RAM, 1 TB SSD, and high end graphics. Keep in mind that higher clock speed is the most important factor in local solve performance, but make sure you have at least 8 cores. More than 8 cores won't make much difference on the kind of solves you are allowed to run locally.
Rob McMillan
Software Architect, Fusion Simulation
Autodesk