I have a Specialized Globe (3 speeds) I bought on craigslist for $150 used. I then got a tune up for $90. I wanted to use it for commuting and did for a while but it felt too slow and the seat is too low. I know very little about bikes and think I spent too much on this. Should I just sell the bike and get one with a bigger frame or buy a taller seat post b/c the current one is way too short? How much do you think this bike is worth? I saw similar bikes on craigslist but not the exact one. I can post a pic of it.

Also, if I buy another bike what are specific things to look for? I’m looking for a sturdy cheap bike that is FAST and would like to get it ASAP. The area I live in has some hills so would it be better to get a bike with more speeds?

Your help is GREATLY appreciated.

Thank you!

Can't offer any guidance without measurements from you and the bike. Pics are nice too. But it doesn't sound like you want help fitting this bike - it sounds like you want help buying a new one.
This is the stuff dreams are made of. Take your measurements, decide how much to spend, go on Craigslist and find something like a rigid MTB that can fit you, and ride it into the dirt.

Yikes, if you think you spent too much on your bike at $240 you're in for a shock to get something better for less money.

The old bike is worth what you can get out of it.

I would suggest going to a local bike shop and get properly fitted and then do them right and buy a bike from them. You will get a warranty and typically some service along with it too. My LBS I bought from does tune ups for life.

As stated above, get your budget figured out and get what you can for that amount of money. If you really stick with it and find yourself riding more and more then in all likelihood you'll find that this bike might not suit your needs in a year or two. Last year I went and bought a brand new hybrid, got exactly what I asked for, a bike with high handlebars and comfort. After about a year I noticed more and more it just wasn't cutting it. I went back this year and bought another one a step up, larger diameter wheels, more gears, a frame size larger, and disc brakes. I love it.

Have you raised the seat to a higher level? If a frame is too small, it is usually too short and you can't adapt an efficient riding position. Globe is a fairly upright style of bike designed for easy riding in flatter cities.
If you need a speedier ride for a hillier commute, look for a lightweight flatbar roadbike style such as the Sirrus. Most other brands make this style as well.
You need 3x8 or 9 gearing, clearance to fit min 28mm tyres+ fenders, threaded eyelets for rack and fenders and a bike that fits you well.
You could get some kind of road bike but the racier kind are less practical, look for one with the features above.

Welcome to the Forums, OP

First, as this topic seems more about finding a new (to you) bike instead of trying to salvage the one you currently have, I merged the duplicate thread in 'Fitting your bike' into this one- cross posting/duplicate threads is kinda frowned upon.

That being said, how tall are you and what size in that Globe 3? You might still be able to make it work as a commuter depending on your answer.

Also, you want to go "fast"... do you have any idea of what speed you are currently reaching? I thought my bike was holding me back from going fast. After I plugged the requisite data into Sheldon's calculator... it ain't the bike that is slow, but the person spinning the cranks