Please check you have chosen the correct gas speed. If the transaction doesn't confirm, you can speed it up or cancel. Please refer to your wallet tutorials for this. Metamask instruction is located here: https://metamask.zendesk.com/hc/en-us/articles/360015489251-How-to-Speed-Up-or-Cancel-a-Pending-Transaction
To receive your pool share (SIG-LP), you have to approve spending your stablecoins (DAI, USDC or USDT), and then deposit them. This means you will sign two or more transactions depending on which stablecoins you deposit.
For example, if you deposit your liquidity only in DAI, you will sign "Approve DAI" and "Deposit DAI" – two transactions in total.
To start farming SIG, you need to approve your SIG-LP tokens and then stake them.
The APY depends on the current amount of staked liquidity – the more users had staked, the less APY will each receive. It also depends on the current token price. Basically, we can't control APY, we can only decide whether to give out more SIG or less.
The price depends on the market - if more people sell SIG than buy, the price might decrease. There are some LPs who sell their SIG rewards right after receiving, and that might shake SIG price in the short-term.