Valery, (1) the correct verb is "strOlling" (2) In English, it sounds strange to use the past progressive in a standalone sentence. We normally only use it when it serves as the backdrop for another action: "Yesterday Tom was strolling in the park WHEN HE HEARD A LOUD BOOM. As it turns out, someone had bombed the central bank."

Yesterday Tom walked to the park

Он гулял не в парк, а в парке.