add linestring to osm streets within postgres

Here is what I did

I have imported streets from OSM into my postgres db with osmosis.

Here is my question

After importing the osm data with osmosis, I now wanna add a linestring to the osm streets. Is there a way to edit the linestring in the existing osm schema/structure that osmosis has defined within postgres

osm data structure within postgres via osmosis

Postgres is showing me following tables:

• nodes
• ways
• way_nodes
• relations
• relation_members

can't figure out the relationship between the tables. I now that the table 'ways' is connected with the table 'way__nodes' via the way_id column.