You should never hurt their feelings.
It could be for any number of reasons ranging from inexperience or partners who were low maintenance or dishonest before you.
Here are 6 things you should do when your partner is bad in bed.
Start with positives
Revel in what s/he already does well and concentrate on that.
Go with small requests
If you like something specific done to you, start small. It could be how you like your back to be stroked a certain way or how you like to make out. Just go with one request at a time.
Never bring it up just before or after sex
That will demoralize your partner and may ruin sex for them for a long time. Keep such conversations away from a sexual situation.
Have that talk in a neutral location
Go to a coffee shop, somewhere neither of your interests could end up dominating the conversation.
Say it by complimenting
Instead of saying they’re doing something wrong, just request for an activity and then offer some guidance, when they get it right, keep it going that way.
If you’re a woman, take over by using woman-on-top positions or using restraints if you have to. When he achieves something, set one of his limbs free as a reward.
If you’re a guy, try taking it slow, seduce her, tease her, get her to tell you what she wants and then play with her. It will lead to mutual satisfaction.
Both can be interchanged depending on your partner’s preferences in bed.