what is lightning network ? how can it solve bitcoin problems ?

The extent of the problem is demonstrated by traders avoiding Bitcoin transactions altogether. It is common to exchange Bitcoin to something that travels way faster and has much lower fees (Litecoin or Ethereum), send it, and then exchange it back to Bitcoin. Moreover, people have had transactions stuck for days, which is like eternity in the cryptosphere. This situation is unacceptable for a coin that has essentially become the face of the cryptocurrency market.

So here comes the lightning network , When Bitcoin was less popular, on-chain transactions were fast and cheap. But as more and more people decided to use Bitcoin, a bottleneck appeared.

Lightning Network can be compared to certificates for Bitcoin ownership. It is much cheaper and faster to exchange certificates than the underying asset. Each certificate is digitally signed by the owner. Instead of burdening the blockchain every time you want to make a small transaction, it will be better to just use LN to send these transactions and redeem them on the actual blockchain only when you need to send a sizeable amount or make a big purchase. And it will be much cheaper that way – one LN transaction is 18,000 times cheaper than a Bitcoin Cash transaction.

The entire Lightning Network is still in the testing stage, but if you are curious and brave you can make small purchases of stickers and t-shirts at the Blockstream store, which already accepts Lightning payments on the Bitcoin mainnet

currently there are now 53 nodes and 83 channels running as you can see it here :
https://lnmainnet.gaben.win/