The Windows file system is actually quite similar to a database. And databases are know to have queries that take much more time than expected. This is also know as an "expensive" query.
If the data inside the filesystem is somehow damaged or stored on slow(er) data blocks from the hard disk, getting something as simple as a menu can take quite some time. It might prove useful to open the command-line and type in there:
CHKDSK C: /F
The command-line version of the Check disk functionality in Windows is much more powerful than the option in Windows itself. The command-line version will ask you to reboot your system. During reboot, your computer will ask if the test should be interrupted. Select here 'No'. After that you will need patience until it is finished. How much patience? That depends on the storage capacity of the drive, the state of the drive, the available resources in your computer etc.
If available, Windows will move file system data around onto faster data blocks as part of the repairs it can execute. And that improves the opening of menus in Windows, because queries have become much "cheaper".
But sometimes a drive has gotten so slow-(ish) that CHKDSK won't help anymore. Tools like 'HD Sentinel Standard' (often offered for free) take a look at the state of your hard disk using S.M.A.R.T., which is functionality built into all hard drives of any type that have been produced the last 20 years or even longer. There are alternative programs for Windows that do the same for free or a small fee.
Still, if your computer is doing tasks in the background, those tasks do consume resources that can make the opening of menus a lot slower as well. It is always a good idea to take a look at what software is running in the background. The Task Manager in Windows 10 has improved a lot when compared with the task manager of previous Windows versions. But there are many freely available alternatives for that as well. None of them can hold a candle against 'Process Explorer' from Sysinternals. It keeps track of many, many things, which may appear to look chaotic in the eyes of someone who is not accustomed to this kind of tool. But when you get your head around it, it is a very good companion in finding out what is bugging your computer. Best of all, it's free.
Process Explorer shows you the load on the CPU, RAM, Network (part of I/O) and drive(s) (also part of the I/O).
High I/O loads seriously slow down any computer. Another test you could try is to kill all running tasks running in the front and background (except Process Explorer) and let the computer 'idle' while keeping an eye on resource usage in Process Explorer. If there is still a high I/O load, you are likely having a piece of hardware in your computer that has degraded. If it is disk I/O, you should consider buying a new drive, if it is network I/O it may be a degraded network module or your system may be infected with a rootkit.