开始 + Noun 我开始了一项新的工作. I started a new job. 我开始 （学） 一本新的汉语课本。 I started (studying) a new Chinese textbook. (not sure if the 学 is required here or not. If include it then its a 开始 + verb + noun structure, but I'm not sure if its correct without). 学 is necessary to clarfy "学" or "写" to aviod the ambiguity. 开始 + Verb 我开始买很多东西。 I started to buy a lot of things.（但是我没有钱！） 我最近开始了减肥。 I've recently started to lose weight. Correction: 我最近开始减肥了. Verb. + 了= the action has finished. Basing this sentence, the action减肥 have not finished. 我拿了他的书. 他做了饭.

开始 can be also used as a noun. If you say this is just a beginning. You should say: 这只是一个开始。 And 开始 also can be referred to the initial stage of process. For example, 刚开始， 他的汉语不怎么好。 That means At the beginning, his Chinese wasn't so good.

When u use 了 in a sentence ,it means a completed action in the past .Like 我吃过饭了 or 我写完作业了....if u wanner to express an action that u have finished ,that's where u can use 了。

Using 了le is easy too. 了le in Chinese is a function word. 1. Verb. / Adj. + 了le = the action and change have completed. 做完了！ 看了电影！ 2. As auxiliary word， 了le is used at the end of sentence or in the sentence, it means something changing. 刮风了，下雨了，打雷了，吃饭了！ 3. 前面两种了le常常出现在同一个句子里。the two usage above always appear in one sentence. 我吃了饭了。 第一个了是完成，第二个了是助词。 first 了 means complete, second is axu.

Thanks. Yes, I guess Noun + 开始 is also good! Like 新的一天开始了 （可是我需要上班 :( :( )