New to 3d printing and have questions

Hi there,
I just purchased a CREALITY ENDER-3 V3 SE 3D PRINTER and have been printing some stuff I have found on Thangs.com. I have a few questions..

First the bottom of the designs seem to be discolored, the one that is on the mat. Is it usually really tough to get the item off the mat? Why is that happening?

Second, I printed some sphero (gyro balls that are suppose to move at each layer. it is a fidget type ball. But in the few I did (different files) the first 2 I could move some of the layers, bu the last one I cannot move any. How can I get them to move? Its like they are glued together. I dont have too many tools yet, as I just ordered a set off Amazon.

Third, some of the files when i put them into the Creality slicer, says they need to have support, what does that mean and how do I add support to print them? I used this site to get it https://www.thingiverse.com/thing:3495390/files and then I downloaded the first one that says sup_V6

Thanks in advance for the help. I am hoping someone can give me some in site on this stuff or point me to some great videos that I can learn from.

Have you leveled the bed ?

First layer hard to remove.........possibly the nozzle is to close to the bed. There should be some way in the slicer or printer control panel to adjust the 'Z' offset, try initially adding plus 0.02mm offset and do a print to see what difference it makes, adjust by 0.01 increments either way until you are happy.

Look on Youtube for videos on getting your first layer right and bed leveling.

Having just got one of these printers, I bought a new bed for it. The supplied one almost welds the prints to it, and its impossible to get off. A lot of the videos on YouTube say the same thing, and suggest its the first thing you should purchase.
I paid $30NZD off aliexpress for a PEI bed and the prints come off a lot easier.

I have printed a few things with movable parts, and its hit an miss whether they are free moving or not, usually i have to score where the gap is with a knife to free them.

Can you send me a link to the bed you purchased? I looked and found many and some are cheaper? I am new at this whole 3d printing thing :)

I purchased this one, was cheap enough and works, seems like a lot come from this company.

Ender 3 V3 SE Upgrade Build Plate PEO/PET/PEY/PEI Sheet 235x235mm Double 3D Printing Platform For Creality Ender3-V3 SE KE

https://a.aliexpress.com/_m07Cjf2

Thanks for the link, sorry I havent check on this for a bit as I have been busy. Can you tell me if it has the metal plate on it so that pretty much when I take it our of the package I can use it? Because I was antsy after I read your message I purchased one on Amazon, but it has an adhesive layer instead of the metal plate, so I am not sure how that works and was going to send it back. Do you have any other tips on tools or any other items I should also purchase from this site?