JMNT(i)
17 Now since some (or: if certain ones) of the branches are broken off (or: were at one point broken out of [the tree]), yet you yourself, being a wild olive tree of the field or forest, you are (or: were) grafted in within (or: among) them, you also came to be (are birthed; are become) a joint-participant (a partner taking in common together with; a co-partaker) of the Root and of the Fatness (= sap) of The Olive Tree (or: of the oil of the olive).
18 Stop boasting against (or: Do not be constantly vaunting or exulting over) the branches! Now since you are habitually boasting and exulting (priding yourself), you yourself are not bearing (supporting; sustaining; carrying) The Root, but rather, The Root you!