in terms of its speed and fees. Will there be any issues
Fees go up when there is a network congestion meaning when there are more transactions than there is block space. It is affected by the number of users not the size of the network. When you say network size it's more about number of nodes that participate in this peer-to-peer network. That has no effect on fees or speed.
No matter how big the network is Bitcoin is able to accumulate it because it has being created and programmed for this purpose and situations like these, so there is nothing to worry about.
Bitcoin is decentralized having thousands of miners in the world and so the network is always secured and strong.
We might not have a high transaction fees unlike what we experienced last year was because the network was filled up and congested with mempool with high fee transactions from the ordinals, NFTs, and BRC20 which cause the increase in transaction, but we might experience high transaction fees before or after the next block halving because they will want to be a partner of the halving. During this period, if you are not ready to pay a higher transaction fee, all you have to do is to combine all your transaction into one to avoid huge fees, but after that period, the price went back to it's normal.