For some reason, English allows you
to turn a prepositional phrase (“My sister made a doll for me”) into an indirect object (“My sister made me a doll”), called a dative shift, or
to turn an active-...
Race as a verb (it may also be a noun) may be transitive or intransitive. The relevant usage in your text is transitive:
1: to compete in a race
2: to go, move,...
There's no problem in general with mixing singular and plural in the same sentence. The only requirement is that the subject and verb need to agree. But a singular subject can take action on plural ...
There are two different issues here: (I) active/passive voice; and (II) prepositions/personal pronouns.
I. Active/Passive Voice:
A doll was made by my sister. (passive voice)
My sister made a doll. (...