Hi,

I'm into bitcoin and crypto for a few years. And getting more and more into this space.

However, there are things that I still don't understand about bitcoin and blockchain in general and I think others will also appreciate learning about.
I hope someone can help me understand the following:

1. Bitcoin block size is limited to 1 MB - right?
So what will happen if the amount of transactions in last 10 minutes will not be able to fit in the block?
Or for example if someone malicious will run a loop script that opens millions / billions of addresses and send them 0.0000001 BTC to clog the system...?

2. As I understand - The blockchain's ledger doesn't have my wallets total amount - it's only documenting the transactions.
So to know how much BTC my wallet has - We have to calculate everything from the beginning of the blockchain, or at least from the first block of my wallet's address - right?
If this is true, how come it's not super slow once the blockchain in very big?


Thanks!