I read this paragraph about if a mining pool controls the majority of the hashrate on the network:
Blocking Transactions:
Anyone who controls the majority of the hashing power can decide which transactions to include in the next block. Due to that, an attacker can even decide to build a completely empty block, with no transactions.
Q.) If I somehow were able to mine a block, how could someone with majority hashing power decide which transactions are included in my block?
If I somehow was able to mine a block, How can someone with majority hashing power can decide transactions to include in my block
Nobody else can influence the contents of the block you are working on.
However, someone with a majority of the mining power will be able to ignore your block, and just work on their own chain instead. Since they have the majority of the hash power, their chain will on average be extended more quickly than the rest of the miners combined, and thus by ignoring your (and all other miners') blocks they will be able to arbitrarily censor transactions. So, it won't matter what transactions you decide to include in your block, since you block will eventually not be a part of the longest (i.e. most work) chain.
