For someone going to the person they love, no hill is an obstacle. The source describes a suitor who visits his beloved's home again and again and is expected to overcome every difficulty in his way.
Source: Gikuyu (Kenya) oral-tradition proverb; "African Proverb of the Month," August 2024 (afriprov.tangaza.ac.ke), where the English is given as "A lover's place has no hills"
The source explains it: The man will visit the girl's home as many times as possible and he is expected to "flatten" as many "hills" as possible. These "hills" include material and moral ones.. The wording of the meaning is ours.