you don't have る ending verb before the くる. It has to be て. so, if it were a 何とかしている　＋　くる => 何とかしていってくる

not totally sure what you are trying to say, so just throwing darts here blindfolded, but... maybe this is what you really wanted? While — ながら (nagara) テレビを見ながら、晩ご飯を食べます。 歩きながら、歌を歌います。 PS. Japanese is highly contextual. If you take out of context just single sentence, it can mean a lot of different things. Whether you mean that you will go, do something and come back or you do something and come to the listener, this depends of the context: are you near the listener at the time or are you not.

てくる　Can in some cases as you mention mean you do something and come back like in　持ってくる But these are kind of set phrases. But it also has other meanings depending on The verb that it follows. For example：　If it follows a verb that takes some time to complete such as わかる、なる、太る、やせる、ふくらむ　Etc.　It will have the meaning of "to begin" or "come to" or "grow to" etc... Very similar to て始める　In meaning.　Example, 最近はちょっと太ってきた。Lately i've started to become fat. Also Continuation of something up to a current point, when used with Non punctual verb Like 読む、勉強する And such it means ＠up until now。　初級では、話し言葉の日本語を中心に勉強してきた at beginner level, up until now you have mainly studied the spoken language. Ha en fin kveld.