Can I copy the "background" and "related work" part of my published paper?

This is called "text recycling" or even "self-plagiarism" and generally frowned upon by editors. It's better to avoid it as much as possible, even if it results in more work, particularly for non-native speakers of English. Too much overlap can result in rejection or later retraction, where "too much" is at the discretion of the editor. You are also very likely to annoy reviewers if they notice the overlap with your previous publications.

The Committee on Publication Ethics has the following guidelines for journal editors:

When should action be considered?

Text recycling can take many forms, and editors should consider which parts of the text have been recycled. Duplication of data is likely to always be considered serious (and should be dealt with according to the COPE guidelines for duplicate publications [1,2]. Use of similar or identical phrases in methods sections where there are limited ways to describe a common method, however, is not uncommon. In such cases, an element of text recycling is likely to be unavoidable in further publications using the same method. Editors should use their discretion when deciding how much overlap of methods text is acceptable, considering factors such as whether authors have been transparent and stated that the methods have already been described in detail elsewhere and provided a citation. Duplication of background ideas in the introduction may be considered less significant than duplication of the hypothesis, discussion, or conclusions.

When significant overlap is identified between two or more articles, editors should consider taking action. Several factors may need to be taken into account when deciding whether the overlap is considered significant.

Text recycling in a submitted manuscript

Text recycling may be identified in a submitted article by editors or reviewers, or by the use of plagiarism detection software, e.g. CrossCheck. Editors should consider the extent of the overlap when deciding how to act. Where overlap is considered to be minor, authors may be asked to re-write overlapping sections, and cite their previous article(s). More significant overlap may result in rejection of the manuscript. Where the overlap includes data, Editors should handle cases according to the COPE flowchart for dealing with suspected redundant publication in a submitted manuscript [1].

There are a number of reasons, besides the obvious legal reasons, why this is a bad idea:

1. If the papers are similar, the referees might be the same. Getting a feeling of déjà vu while refereeing feels very bad. Experts analyze a paper in terms of how it is different from the existing literature. If it cannot be separated from this literature, things get muddy.

2. Your previous write-up was probably not yet perfect. A researcher is, at least partly, paid for writing papers and is, therefore, a professional writer. Use the chance to improve your writing.

3. Even if what you wrote before is perfect, it would only be perfect in the context of the questions addressed in the previous paper. Even if you are talking about the same algorithms and the same papers by other authors, they will relate differently to the present contribution of the current paper. A well-written paper is not a badly fitting collection of parts like Frankenstein's monster but tightly integrated. Work on the coherence of the paper.

Another legal reason for publishers requiring you to rewrite this material is that the copyright holder on the previous paper (which is most likely the publisher, not you!) might object to another publisher violating their copyright on the recycled text.