While in sunlight, the Dhampir has disadvantage on Attack Rolls, as well as on Wisdom (Perception) checks that rely on sight.

A Dhampir gains a +1 to Dexterity from their Vampire's counterpart, and another bonus from the other parent's races. 

From their Vampire parent, a Dhampir has good hearing, smell and sight.

The Dhampir is not affected by difficult terrain can climb difficult surfaces, without needing to make an ability check. This doesn't mean they can stand on walls.

Upon reaching level 3, If the Dhampir isn't in sunlight or running water,  once per long rest it can use its action to polymorph into a Tiny bat.

While in bat form, they can't speak, they're walking speed is 5 feet, and they has a flying speed of 30 feet. Its mental statistics, other than its size and speed, are unchanged. Anything they is wearing transforms with them, but nothing they is carrying does. It reverts to its true form if they HP goes to 0 or after 1minute/level of duration. 

You know the Chill Touch cantrip. When you reach 3rd level, you can cast the command spell as a 2nd-level spell once with this trait and regain the ability to do so when you finish a long rest. When you reach 5th level, you can cast the ray of enfeeblement spell once with this trait and regain the ability to do so when you finish a long rest. Charisma is your spellcasting ability for these spells.