Probably the 100th same staking question asked

So I’ve looked for the answer to this question but can’t really find it and I know it’s probably been asked here a lot. If I stake my eth can i also add to it monthly? Also, can I add eth that I don’t have to stake so I can mess around without it being fixed for two years? For example I’d have 2,000 staked that I would add 300 to every month, then also 1000 unstaked. Is this possible?