I still use my MacBook Pro 2011 on a daily basis and it’s going strong. 2 things you can do to speed it up.
First, the simplest thing to do is see what programs are starting up in the background that don’t need to and address that. You can review how to do that here.
Second, and this is where the real bang for your buck will come in, you can swap out your hard drive for a solid state drive. Oddly enough, those 2011 MacBook Pros come with a SATA3 controller on the motherboard, but only come with a SATA2 drive.
So, upgrading to a SSD not only gives you the improved performance of solid state, it also doubles the data transfer rate between the drive and the board.
When I upgraded mine, waking up my Mac from sleep went from 1 minute 26 seconds to 10 seconds. Everything got so much faster I no longer even thought about a new laptop.
Also, if you want to keep it for a while, you can upgrade the standard 4 GB of RAM to 16 GB.
I would imagine you could do all of that for < $150, depending on the size of the SSD you get and whether or not you choose to do it yourself.