Will bitcoin not work any more? I am not an expert on bitcoin, so please pardon me for dumb questions. 

1, Will bitcoin not work any more in the far future? I think, not sure, every bitcoin transactions are recorded into memory or a block, and since this memory is so limited and hard to get, let's assure that your memory card is full or corrupted, then your expensive digital camera simply won't work anymore. So I think bitcoin owners pay too much on their memory card and forget about that the real value is in the camera. 

2, What are the differences between a bitcoin and a memory block? I think they are the same thing, but on the other hand, I can spend a bitcoin, but I don't think I can spent a memory block.

3, I notice a payment that I sent days ago still haven't got confirmed. I sent 0.003 BTC and the fee I pick is 0.0003 BTC which was all I got in my wallet. That is too slow. I understand why, but I just can't accept it. So my third question will be what happen when everyone pick the same "priority" or Sat/b value, how long will it take for a transaction to go through in this unrealistic scenario?

4, It's basic economy, Supply and Demand. Since people are paying priority fee every new day, why would anyone want to process the lower fee transactions at all? 

5, Is bitcoin really decentralized? but how can anything be decentralized when it's controlled by a group of people, namely those with a super computer. Well, it sorts of like the internet. Internet is controlled by few huge tech companies, some even controlled by its government.
I will try to respond to what I've understood about your question. Correct me if I miss your point.

1

Transactions are stored inside blocks in the blockchain. The blockchain is a distributed database, stored on thousands of computers around the world. This means that corrupted memory on a node won't affect the net, because the same information is on every other "sane" machine. It is true though that the size of such database is ever increasing and less people want to become full nodes for the size of it. Memory is not limited and is not hard to get (in this case). The current dimension of the blockchain is of about 140 GB and almost anyone can affort a 1 TB Hard Disk. Your camera (your bitcoin's) won't be useless if you fill up every tiny byte of memory in your machine because the same data will be in every node in the network

2

When you want to send bitcoins you create a transaction.

A group of transaction is put together to form a block.

Therefore you can't spend blocks, because they are just a data structure.

So bitcoins are just numbers sent and received by people. Blocks are the structures that contain the information about the excange if bitcoins between people.

3/4

A transaction's priority is based on its fee and the time elapsed from the moment it was sent to the network. The older a transaction is, the more priority it has.
So if you send a transaction with a low fee then you should be prepared to wait a long time (days) until it will get confirmed. If the fee is extremely low, it may occurr that the transaction won't get through for years!.

A fee of 0.0003 is a bit low. I understand that you had 0.0033 BTC and sent 0.003 and paid another 0.0003 as a fee.

5

It was born as super decentralized and now it's becoming less decentralized because of the difficulties bounded with running a full node and mine. We will se what the future holds for us.

Note
I suggest you read some basic article about Bitcoin (you can find a lot of them just looking at the first results of a google search) to understand the basics

read this

FROM THE START

I'll try to explain you in a simple way how Bitcoin works.

Bitcoins is a peer to peer network that organizes the excange of data between people using a chain of blocks. This chain is protected by cryptography and every node shares the same chain. That chain of blocks is just a bunch of data files. Whenever two people want to send bitcoin between themselves in the blockchain they create a transaction, which then is included in a block by a miner. The miner gets a reward for creating the block (which costs computing power) and the fees attached to the transactions. The block he creates is just a simple plain old file, it is not some sort of magical and costly paper. Every block can at most be 1MB in size so it isn't storage demanding either. 

As for the price of bitcoins it only depends on how much people are willing to pay them. If everyone wants a bitcoin then the price goes up. If no one wants a bitcoin the price goes down (to put it in an exaggeratly simple way).