Yes But No But...
Setting sexual boundaries with your partner
Great sex isn't about agreeing to everything your partner wants. Different people like different things and there's no right or wrong: it's about finding things that you enjoy together.
Some people will ask you to do things you don't want to do. Never do anything that you don't want to - it doesn't make you a prude or a bad lover. It just means you're confident enough to be honest. If a partner judges you for saying no, they may not have your best interests at heart. Better to ditch a pushy partner than do something that makes you feel bad. This goes doubly if they try to persuade you to have unsafe sex.
Women often take longer to come than men do. You might be tempted to fake it or forget your own pleasure but this can lead to resentment and loss of libido - and make your partner feel insecure too. The easiest way to help your partner make you come is to demonstrate: masturbate like you do when you're alone. If you feel shy, you may find it easier if it's mutual, so you can learn about your partner at the same time.
If a partner judges you for saying no, they may not have your best interests at heart.
You can also take matters into your own hands. Everyone has responsibility for their own orgasm (though a good lover cares about their partner's pleasure) and touching yourself or using a toy together can help you both get off.
If your partner doesn't seem to care about your pleasure, don't immediately write them off. They may be insecure about what you like (which is why masturbating together can be so useful). Talk about what you enjoy. However, if a lover still doesn't make an effort, do think whether you really want to be with them. Sex is about two people, not one, after all.