atta(あった)... past form of copula "aru(ある)".
"Soko ni wa kouen ga atta."
"There(soko ni wa) used to be(atta) a park(kouen)."
It is often used with "... de(で)", so "... de-atta(であった)" means "was."
"Watashi wa oroka de-atta."
"I(watashi) was(wa ... de-atta) fool(oroka)."
* do not confuse, another single word "deatta(であった/出会った)" means "met".
It is the past form of "deau(であう/出会う)".
"Kare wa sann-nenn-mae, kanojo ni deatta."
"He(kare) met(ni deatta) her(kanojo) three(sann) years(nenn) ago(mae)."
Sorry I must leave now, rest questions shall be answered later.
I use Roman alphabet.
1.
sugiru : (すぎる/過ぎる)… it's originally a verb, SUGIRU, but in the same form it can be used as adverb , meaning "too ...".
"Sono mondai wa watashi ni wa mutsukashi sugiru."
"The(sono) problem(mondai) is(wa) too(sugiru) difficult(mutsukashi) for(ni) me(watashi)."
nagara: (ながら/乍ら)... it means "... during/while ..." or "but".
Verb[Rennyou-form] + nagara : "Shukudai shi-nagara TV wo miru."
"I watch(miru) TV do(shi-)ing(nagara) homeworks(shukudai)."
with "shikashi(しかし/然し)", "shikashi-nagara(しかしながら)", the "nagara" part only emphasis the "shikashi".
"Sore wa naruhodo sou da, shikashi-nagara, genjitsu wa sou wa ikanai."
"Indeed it is, but(shikashi-nagara) we cannot do in practice."