Learn Hardcore Hausa: Da yamma ina karanta littafi a ƙarƙashin bishiya a waje. - In the evening I read a book under a tree outside.

Da yamma is an idiomatic time phrase meaning in the evening / at evening time. Hausa often uses da with parts of the day, e.g. da safe (in the morning), da rana (in the daytime), da yamma (in the evening). It’s best learned as a set pattern.

Why does the sentence start with the time phrase? Is that the normal word order?

Yes. Hausa commonly places a time expression first for context: Da yamma + clause. You could also put it later, but starting with time is very natural and frequent.

Does ina karanta mean I read or I am reading?

In this kind of sentence, ina karanta is the continuous/progressive: I am reading (at that time). In some contexts it can feel more general, but the most straightforward reading here is ongoing action.

Is ina a pronoun? I thought ina? means where?

Two different things:

ina (with a verb after it) is a 1st person singular subject + continuous marker: ina karanta = I am reading.
ina? by itself is the question word where? Context (and the presence/absence of a following verb) tells you which one it is.