First of all you need to understand that in the early 1100's there wasn't really the concept that we nowadays call "nation-state", so to call D. Henrique as "foreigner" doesn't really have the same implications as today.

With that being said, lets get to the bottom of this.

D. Afonso Henriques was as you said, the son of Count D. Henrique and Princess Teresa of Leon (although there are some suspicions that he was in fact the son of Egas Moniz, a portuguese nobleman, those suspicions are not really taken seriously). His place of birth is disputed but he was most likely born and raised in Guimarães which would later become the administrative capital of the fledgling kingdom.

He was raised by Portuguese noblemen, and most of the people he would have contact with would be very similar culturally. For the most part, his powerbase was rooted in culturally portuguese noblemen, not in frankish or german assistance.

This does not mean that northern european assistance wasn't used, you mentioned the conquest of Lisboa, and that wasn't the only conquest where english, french, german, etc.. knights were a key part of the Reconquista, however such assistance was mainly focused on fighting the moors. For the most part, they came for a religious war, not a political war between 2 christian nations.

It's not unreasonable therefore, given that his father died when he was 4 and that he was raised by culturally portuguese noblemen, to say that "foreign" influence in terms of culture would be minimal.

Here are a few documents you can read if you know portuguese.

This is probably the most relevant since it speaks of portuguese nobility in the peninsular context

This speaks a bit of how he was raised, and his main efforts

This one talks about Egas Moniz who was a very big influence throughout his life