is this paragraph on bitcoin correct?
There are a number of badly worded or misconceptions in there, but in future it would be better to ask specific questions rather than posting an entire description of bitcoin and asking if it is right :)


  and why validation of a transaction takes on average 60 minutes if everything goes well


This is slightly badly worded, validation of the transaction is easy (just makes sure its a valid transaction spending valid inputs). Its confirming it which you might like to take up to an hour for, but technically you don't have to wait for confirmations if you want to sacrifice a bit of security for speed (1 confirmation should be plenty for smaller purchases). 


  it used to be 25 BTC


Note that it started at 50, this makes it sound like it started at 25.


  an easy part: a list of transactions since the last block was found, this is to validate the transactions.


The block just has a list of the transactions in the block. Your wording sounds weird, and it doesn't necessarily include all transactions since the last block, just the ones picked by the miner.


  a difficult part: a code that proves the identity of the miner that mined it (so that the network can award him the 12.5 BTC). 


The miner doesn't prove their identity. They just include a special coinbase transaction in the block which pays the block reward to an address of their choice. And the block hash isn't really a "code", its just a valid block.


  at defined rate every 10min


The 10 minutes is just an average, the difficulty of finding a valid block changes to adjust for hashpower changes every 2016 blocks. You mention this, but you make it sound like somehow the decreasing supply of bitcoin per block is related to it. Its not, the difficulty just depends on how quickly the last 2016 blocks were found (technically 2015, due to an off-by-one error in the code).


  Now the problem is that there is since origin a limitation in the size of each block: 1Mb. This corresponds to ~ only 3 transactions by second. If the transaction rate goes significantly higher, it will create further delays in the validation process. This is the reason of the bitcoin forks.


This is outdated, it ignores the changes by segwit such as block weight instead of size, and the softfork to a maximum of 4Mb blocks. And where did that 3tx/s number come from? Also, the forks are hugely political in nature, you're oversimplifying.